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Computer science what are Euler circles. Euler circles: why seeing once is better than hearing a hundred times

Material overview

Mathematics is one of my favorite subjects in high school. I like to solve different mathematical puzzles, logical problems. At the math circle, we get acquainted with various ways of solving problems. Once, in the classes of a circle, we were asked to solve the following problem at home: “There are 35 students in the class, 12 are engaged in a mathematical circle, 9 in a biological circle, and 16 children do not attend these circles. How many biologists are into mathematics? I solved it like this:

35 - 16 = 19 (guys) - attend circles

19- 9 = 10 (children) - attend a math circle

12 - 10 = 2 (biologist) - are fond of mathematics.

And she asked me to check the solution of the older brother's problem. He said that

The problem is solved correctly, but there is a more convenient and faster way to solve it. It turns out that the so-called Euler circles help to simplify the solution of this problem, with the help of which you can depict a set of elements that have a certain property. I was interested in a new way of solving the problem and I decided to write a research paper on the topic: "Problem solving using Euler circles"

I set a goal for myself: to learn a new way to solve non-standard problems using Euler circles.

For the disclosure of the topic of my research work, the following tasks were set:

Learn to use scientific literature.

Learn what Euler circles are.

Create an algorithm for solving problems.

Learn how to solve problems using Euler circles.

Make a selection of tasks for use in the classroom of a mathematical circle.

Research methods:

Study and analysis of scientific literature;

Method of inductive generalization, concretization.

Object of study: Euler circles

Subject of research: the concept of a set, the main actions with them necessary when solving problems using Euler circles

Participants of the study: students in grades 5-9 of the gymnasium

Research hypothesis: The Euler method simplifies reasoning in solving some problems and facilitates the path to its solution.

The relevance of the study lies in the fact that there are many techniques and methods for solving non-standard logical problems. Often, when solving a problem, drawings are used, which makes the solution of the problem simpler and more visual. One of such visual and convenient ways to solve problems is the Euler circle method. This method allows solving problems with a cumbersome condition and with many data.

Problems solved with the help of Euler circles are very often offered at mathematical Olympiads. Such tasks often have a practical nature, which is important in modern life. They make you think and approach the solution of a problem from different angles. Learn to choose from a variety of ways the most simple and easy.

Theoretical part

Brief historical background.

Leonard Euler (1707-1783) - the great mathematician of the St. Petersburg Academy of the 18th century. Born in the Swiss town of Basel. Early discovered mathematical abilities. At the age of 13, he became an art student at the University of Basel, where both mathematics and astronomy were taught. At the age of 17 he was awarded a master's degree. At the age of 20, Euler was invited to work at the St. Petersburg Academy of Sciences, and at 23 he was already a professor of physics, three years later he received the department of higher mathematics.

Leonhard Euler, during his long life, left the most important works in various branches of mathematics, mechanics, physics, astronomy and a number of applied sciences, wrote more than 850 scientific papers. In one of them, these circles appeared.

What are Euler circles?

I found the answer to this question by reading various cognitive literature. Leonhard Euler believed that "circles are very suitable for facilitating our reflections." When solving a number of problems, he used the idea of depicting sets using circles, which is why they were called “Euler circles”.

In mathematics, a set is a collection, a set of any objects (objects). The objects that make up a set are called its elements. It is conditionally accepted that the circle clearly depicts the volume of one of some concepts. For example, our 5th grade is a set, and the number of students in a class is its elements.

In mathematics, sets are denoted by capital Latin letters, and their elements by capital letters. Often written in the form A = (a, b, c, ...), where the elements of the set A are indicated in curly brackets.

If each element of the set A is at the same time an element of the set B, then we say that A is a subset of the set B. For example, the set of students of the 5th grade of our gymnasium is a subset of all students of the gymnasium.

With sets, as with objects, you can perform certain actions (operations). In order to more clearly imagine actions with sets, special drawings are used - Euler diagrams (circles). Let's get acquainted with some of them.

The set of common elements A and B is called the intersection of the sets A and B and is denoted by the sign ∩.

A ∩ B = (m), C ∩ B = (e, u).

The sets A and C do not have common elements, so the intersection of these sets is the empty set: A ∩ C = ∅.

If from the elements of the sets A and B we compose a new set consisting of all the elements of these sets and not containing other elements, then we get the union of the sets A and B, which is denoted by the sign ∪.

Consider an example: Let A \u003d (t, o, h, k, a), B \u003d (t, u, p, e), C \u003d (d, e, f, u, c).

A∪B = (t, o, h, k, a, u, p, e), B∪ C = (t, u, p, e, d, f, s), A ∪ B ∪ C = (t , o, h, k, a, i, p, e, e, f, s).

Conclusions: Euler circles are a geometric scheme that allows you to make logical connections between phenomena and concepts more visual. It also helps to depict the relationship between any set and its part.

You can verify this with an example task.

All my friends grow some kind of flowers in their apartments. Six of them breed cacti, and five violets. And only two have both cacti and violets. How many girlfriends do I have?

Let's determine how many sets are in the problem (i.e. how many circles we will draw when solving the problem).

In the problem, my friends grow 2 types of flowers: cacti and violets.

This means the first set (1 circle is friends who grow cacti).

The second set (circle 2 are friends who grow violets).

In the first circle we will denote the owners of cacti, and in the second circle, the owners of violets.

Select a condition that contains more properties to draw the circles. Some friends have both of these flowers, then we will draw circles so that they have a common part.

Let's do the drawing.

In the general part, we put the number 2, since two friends have both cacti and violets.

According to the condition of the problem, 6 friends breed cacti, and 2 are already in the common part, then in the rest of the cacti we put the number 4 (6-2 \u003d 4).

5 friends are breeding violets, and 2 are already in the common part, then in the remaining part of the violets we put the number 3 (5-2 \u003d 3)

The picture itself tells us the answer 4+2+3=9. We write down the answer.

Answer: 9 friends

Practical part

Solving problems using Euler circles

Having figured out what the Euler circles are on the example of the problem and the material studied, I decided to move on to compiling an algorithm for solving problems using this method.

2.1 Algorithm for solving problems

We carefully study and briefly write down the condition of the problem.

We determine the number of sets and label them.

Let's do the drawing. We construct the intersection of sets.

We write the initial data in circles.

Select the condition that contains more properties.

We write the missing data in Euler circles (reasoning and analyzing)

We check the solution of the problem and write down the answer.

Having compiled an algorithm for solving problems using Euler circles, I decided to work it out on several more problems.

Problems on the intersection and union of two sets

Task 1.

There are 15 students in my class. Of these, 9 are engaged in the athletics section, 5 in the swimming section and 3 in both sections. How many students in the class do not attend sections?

Solution.

The problem has one set and two subsets. Round 1 - total students. 2 circle - the number of students involved in athletics. 3 circle - the number of students involved in swimming.

We will depict all students using a larger circle. Inside we will place smaller circles, and draw them so that they have a common part (since three guys are engaged in both sections).

Total

Let's do the drawing.

There are 15 students inside the big circle. In the general part of the smaller circles we put the number 3. In the rest of the circle l / a we put the number 6 (9-3=6). In the rest of the circle n - put the number 2 (5-3=2).

5. We write down the answer according to the picture: 15-(6+3+2) = 4 (students) are not engaged in any of these sections.

Problem 2. (which I solved in a different way, but now I will solve it using Euler circles)

There are 35 students in the class, 12 are engaged in a mathematical circle, 9 in a biological one, and 16 children do not attend these circles. How many biologists are into mathematics?

Solution:

The problem has one set and two subsets. Round 1 - total students in the class. 2 circle the number of students involved in a mathematical circle (denoted by the letter M). 3 circle - the number of students involved in the biological circle (denoted by the letter B).

Let's depict all the students in the class using a large circle. Inside we place smaller circles that have a common part, because several biologists are fond of mathematics.

Let's do the drawing:

There are only 35 students inside the big circle. 35-16 = 19 (students) attend these circles. Inside the circle M we put 12 students involved in a mathematical circle. Inside circle B we put 9 students involved in a biological circle.

Let's write down the answer from the picture: (12 + 9) - 19 = 2 (students) - they are fond of biology and mathematics. Answer: 2 students.

2.3. Problems for the intersection and union of three sets

Task 3.

There are 40 students in the class. Of these, 19 people have “triples” in Russian, 17 people in mathematics and 22 people in history. Only in one subject have “triples”: in Russian - 4 people, in mathematics - 4 people, in history - 11 people. Seven students have “triples” in both mathematics and history, and 5 students have “triples” in all subjects. How many people study without "triples"? How many people have "triples" in two of the three subjects?

Solution:

The problem has one set and three subsets. 1 large circle - total students in the class. Circle 2 is the number of students with triples in mathematics (denoted by the letter M), circle 3 is smaller - the number of students with triples in the Russian language (denoted by the letter P), circle 4 is smaller - the number of students with triples in history (denoted by the letter I)

Let's draw the Euler circles. Inside the larger circle depicting all the students in the class, we place three smaller circles M, R, I, meaning mathematics, Russian language and history, respectively, and all three circles intersect, since 5 students have "triples" in all subjects.

Let's write the data in circles, reasoning, analyzing and performing the necessary calculations. Since the number of children with "triples" in mathematics and history is 7, then the number of students with only two "triples" - in mathematics and history, is 7-5 = 2. Then 17-4-5-2=6 students have two "triples" - in mathematics and in Russian, and 22-5-2-11=4 students have only two "triples" - in history and in Russian. In this case, 40-22-4-6-4 = 4 students study without a “troika”. And they have “triples” in two subjects out of three 6 + 2 + 4 = 12 people.

7-5=2 - the number of students who have only two "triples" - M, I.

17-4-5-2=6 - the number of students who have only two "triples" - M, R.

22-5-2-11=4 - the number of students with only two "triples" - I, R.

40-22-4-6-4=4 - the number of students studying without a "troika"

6 + 2 + 4 = 12 - the number of students with "triples" - in two subjects out of three

Answer: 4 students study without “triples”, 12 students have “triples” in two subjects out of three

Task 4.

There are 30 people in the class. 20 of them use the subway every day, 15 use the bus, 23 use the trolleybus, 10 use both the subway and trolleybus, 12 use both the subway and bus, 9 use both the trolleybus and the bus. How many people use all three modes of transport every day?

Solution. 1 way. For the solution, we again use the Euler circles:

Let x person use all three modes of transport. Then only the metro and trolleybus - (10 - x) people, only the bus and trolleybus - (9 - x) people, only the metro and bus - (12 - x) people. Let's find how many people use the metro alone:

20 - (12 - x) - (10 - x) - x = x - 2

Similarly, we get: 15 - (12 - x) - (9 - x) - x \u003d x - 6 - only by bus and

23 - (9 - x) - (10 - x) - x \u003d x + 4 - only by trolleybus, since there are only 30 people, we make the equation:

X + (12 - x) + (9 - x) + (10 - x) + (x + 4) + (x - 2) + (x - 6) = 30. hence x = 3.

2 way. And you can solve this problem in another way:

20+15+23-10-12-9+x=30, 27+x=30, x=3.

Answer: 3 people use all three modes of transport every day.

2.4. Drawing up tasks of practical importance

Task 1. There are 15 people in class 5A. 5 people go to the Erudite circle, 13 people go to the Path to the Word circle, 3 people attend the sports section. Moreover, 2 people attend the "Erudite" circle and the "Way to the Word" circle, "Erudite" and the sports section, the sports section and the "Way to the Word". How many people attend all three circles?

Solution:

1. Let x people attend all three circles, then

2. 5+13+3-2-2-2+x=15, 13+x=15, x=2

Answer: 2 people attend all three circles.

Task 2

It is known that 6B grade students are registered in social networks: VK, Odnoklassniki, Dating Galaxy. 2 students are not registered in any social network, 7 students are registered in both Odnoklassniki and VK; 2 students only in Odnoklassniki and 1 only in VK; and 2 students are registered in all 3 social networks. How many class members are registered in each social network? How many class members took part in the survey?

Solution:

Using the Euler circles, we get:

1+5+2=8 people are registered in VK,

In Odnoklassniki 2+5+2=9 people,

There are only 2 people in the Galaxy of Dating.

A total of 1+5+2+2+2=12 people took part in the survey

2.5. Tasks for use in the classroom of a mathematical circle

Task 1: "Harry Potter, Ron and Hermione"

There were 26 magical spellbooks on the shelf, all of them had been read. Of these, 4 were read by both Harry Potter and Ron. Hermione read 7 books that neither Harry Potter nor Ron read, and two books that Harry Potter read. Harry Potter has read 11 books in total. How many books has Ron alone read?

Task 2: "Pioneer camp"

Task 3: "Extreme"

Of the 100 children who go to the children's health camp, 30 children can snowboard, 28 can skateboard, and 42 can roller skate. - 5, and on all three - 3. How many guys do not know how to ride a snowboard, or a skateboard, or rollerblading?

Task 4: "Football team"

The Spartak football team has 30 players, including 18 forwards, 11 midfielders, 17 defenders and goalkeepers. It is known that three can be attackers and defenders, 10 defenders and midfielders, 6 attackers and defenders, and 1 attacker, defender and midfielder. Goalkeepers are irreplaceable. How many goalkeepers are on the Spartak team?

Task 5: "Shop"

The store was visited by 65 people. It is known that they bought 35 refrigerators, 36 microwaves, 37 televisions. 20 of them bought both a refrigerator and a microwave, 19 a microwave and a TV, 15 a refrigerator and a TV, and all three purchases were made by three people. Was there a visitor among them who did not buy anything?

Task 6: "Kindergarten"

There are 52 children in the kindergarten. Each of them loves either cake, or ice cream, or both. Half of the children love cake, and 20 people like cake and ice cream. How many kids love ice cream?

Task 7: "Student Brigade"

There are 86 high school students in the student production team. 8 of them do not know how to work either on a tractor or a combine. 54 students mastered the tractor well, 62 - the combine. How many people from this team can work both on the tractor and on the combine?

Research part

Purpose: the use of the Euler method by students of the gymnasium in solving non-standard problems.

The experiment was conducted with the participation of students in grades 5-9 who are fond of mathematics. They were asked to solve the following two problems:

From the class, six students go to a music school, and ten are engaged in the football section, ten more attend the art studio. Three of them attend both football and music school. How many people are in the class?

The store was visited by 65 people. It is known that they bought 35 refrigerators, 36 microwaves, 37 televisions. 20 of them bought both a refrigerator and a microwave, 19 bought both a microwave and a TV, 15 bought a refrigerator and a TV, and all three purchases were made by three people. Was there a visitor among them who did not buy anything?

The first task out of 10 participants (2 people from each parallel of classes) of the experiment was solved only by 4 people, the second only by two (moreover, students of grades 8 and 9). After I presented them with my research work, in which I talked about Euler circles, analyzed the solution of several simple and proposed problems using this method, students could solve simple problems themselves.

At the end of the experiment, the children were given the following task:

There are 70 children in the pioneer camp. Of these, 27 are involved in a drama circle, 32 sing in a choir, 22 are fond of sports. There are 10 guys from the choir in the drama club, 6 athletes in the choir, 8 athletes in the drama club; 3 athletes attend both the drama circle and the choir. How many guys don't sing, don't go in for sports, don't play in a drama circle? How many children are engaged only in sports?

Of the 10 participants in the experiment, all coped with this task.

Conclusion: Solving problems using Euler circles develops logical thinking, makes it possible to solve problems that can be solved in the usual way only when compiling a system of three equations with three unknowns. Students in grades 5-7 do not know how to solve systems of equations, but they can solve the same problems. So the guys need to know this method of solving problems using Euler circles.

Applications May 28, 2015

Leonhard Euler (1707-1783) - famous Swiss and Russian mathematician, member of the St. Petersburg Academy of Sciences, lived most of his life in Russia. The most famous in mathematical analysis, statistics, computer science and logic is the Euler circle (Euler-Venn diagram), used to denote the scope of concepts and sets of elements.

John Venn (1834-1923) - English philosopher and logician, co-inventor of the Euler-Venn diagram.

Compatible and incompatible concepts

A concept in logic means a form of thinking that reflects the essential features of a class of homogeneous objects. They are denoted by one or a group of words: “world map”, “dominant fifth-seventh chord”, “Monday”, etc.

In the case when the elements of the scope of one concept fully or partially belong to the scope of another, one speaks of compatible concepts. If, however, no element of the scope of a certain concept belongs to the scope of another, we have incompatible concepts.

In turn, each of the types of concepts has its own set of possible relations. For compatible concepts, these are the following:

identity (equivalence) of volumes;
intersection (partial coincidence) of volumes;
subordination (subordination).

For incompatible:

subordination (coordination);
opposite (contrararity);
contradiction (contradiction).

Schematically, the relationship between concepts in logic is usually denoted using Euler-Venn circles.

Equivalence relations

In this case, the terms mean the same subject. Accordingly, the volumes of these concepts are completely the same. For example:

A - Sigmund Freud;

B is the founder of psychoanalysis.

A - square;

B is an equilateral rectangle;

C is an equiangular rhombus.

Completely coinciding Euler circles are used for designation.

Intersection (partial match)

A - teacher;

B is a music lover.

As can be seen from this example, the volumes of concepts partially coincide: a certain group of teachers may turn out to be music lovers, and vice versa - there may be representatives of the teaching profession among music lovers. A similar attitude will be in the case when, for example, “citizen” acts as concept A, and “driver” acts as B.

Subordination (subordination)

Schematically denoted as Euler circles of different scales. The relationship between concepts in this case is characterized by the fact that the subordinate concept (smaller in volume) is completely included in the subordinate (larger in volume). At the same time, the subordinate concept does not completely exhaust the subordinate one.

For example:

A - tree;

B - pine.

The concept B will be subordinate to the concept A. Since the pine tree belongs to the trees, the concept A becomes in this example the subordinate, “absorbing” the scope of the concept B.

Subordination (coordination)

Attitude characterizes two or more concepts that exclude each other, but at the same time belong to a certain common generic circle. For example:

A - clarinet;

B - guitar;

C - violin;

D is a musical instrument.

Concepts A, B, C are not intersecting in relation to each other, however, they all belong to the category of musical instruments (concept D).

Opposite (contrary)

Opposite relationships between concepts imply that these concepts belong to the same genus. At the same time, one of the concepts has certain properties (features), while the other denies them, replacing them with opposite ones in character. Thus, we are dealing with antonyms. For example:

A - dwarf;

B is a giant.

The Euler circle with opposite relations between concepts is divided into three segments, the first of which corresponds to the concept A, the second - to the concept B, and the third - to all other possible concepts.

Contradiction (contradiction)

In this case, both concepts are species of the same genus. As in the previous example, one of the concepts indicates certain qualities (features), while the other denies them. However, in contrast to the relation of opposites, the second, opposite concept does not replace the denied properties with other, alternative ones. For example:

A is a difficult task;

B is an easy task (not-A).

Expressing the volume of concepts of this kind, the Euler circle is divided into two parts - the third, intermediate link in this case does not exist. Thus, the concepts are also antonyms. In this case, one of them (A) becomes positive (affirming some feature), and the second (B or non-A) becomes negative (negating the corresponding feature): “white paper” - “not white paper”, “national history” - "foreign history", etc.

Thus, the ratio of the volumes of concepts in relation to each other is the key characteristic that defines the Euler circles.

Relationships between sets

It is also necessary to distinguish between the concepts of elements and sets, the volume of which is displayed by Euler circles. The concept of a set is borrowed from mathematical science and has a fairly broad meaning. Examples in logic and mathematics display it as a certain set of objects. The objects themselves are elements of this set. “Many is many thought as one” (Georg Kantor, founder of set theory).

The designation of the sets is carried out in capital letters: A, B, C, D ... etc., the elements of the sets - lowercase: a, b, c, d ... etc. Examples of the set can be students in the same classroom, books standing on a certain shelf (or, for example, all the books in a certain library), pages in a diary, berries in a forest clearing, etc.

In turn, if a certain set does not contain a single element, then it is called empty and denoted by the sign Ø. For example, the set of intersection points of parallel lines, the set of solutions to the equation x 2 = -5.

Problem solving

Euler circles are actively used to solve a large number of problems. Examples in logic clearly demonstrate the connection between logical operations and set theory. In this case, truth tables of concepts are used. For example, the circle labeled A represents the truth region. So the area outside the circle will represent false. To determine the diagram area for a logical operation, you should shade the areas that define the Euler circle in which its values for elements A and B will be true.

The use of Euler circles has found wide practical application in various industries. For example, in a situation with a professional choice. If the subject is concerned about the choice of a future profession, he can be guided by the following criteria:

W - what do I like to do?

D - what do I get?

P - how can I make good money?

Let's depict this in the form of a diagram: Euler circles (examples in logic - the intersection relation):

The result will be those professions that will be at the intersection of all three circles.

Euler-Venn circles occupy a separate place in mathematics (set theory) when calculating combinations and properties. The Euler circles of the set of elements are enclosed in the image of a rectangle denoting the universal set (U). Instead of circles, other closed figures can also be used, but the essence of this does not change. The figures intersect with each other, according to the conditions of the problem (in the most general case). Also, these figures should be labeled accordingly. The elements of the sets under consideration can be points located inside different segments of the diagram. Based on it, specific areas can be shaded, thereby designating the newly formed sets.

With these sets, it is permissible to perform basic mathematical operations: addition (sum of sets of elements), subtraction (difference), multiplication (product). In addition, thanks to the Euler-Venn diagrams, it is possible to compare sets by the number of elements included in them, without counting them.

Solving logic problems using Euler circles

Euler circles- problems on the intersection or union of sets This is a new type of problems in which it is required to find some intersection of sets or their union, observing the conditions of the problem.

Euler circles - a geometric diagram with which you can depict the relationship between subsets, for visual representation. Euler's method is indispensable for solving some problems, and also simplifies reasoning. However, before proceeding to solve the problem, it is necessary to analyze the condition. Sometimes it is easier to solve a problem with the help of arithmetic operations.

Task 1. There are 35 students in the class. Of these, 20 people are engaged in a mathematical circle, 11 in a biological one, 10 children do not attend these circles. How many biologists are into mathematics?

Let's depict these circles in the figure. We can, for example, draw a large circle in the school yard, and two smaller circles in it. Into the left circle marked with the letter M, we put all mathematicians, and in the right one, denoted by the letter B, all biologists. Obviously, in the general part of the circles, indicated by letters MB, there will be those very biologists-mathematicians who are of interest to us. We will ask the rest of the guys in the class, and there are 10 of them, not to leave the outer circle, the largest one. Now let's calculate: there are 35 guys inside the big circle, 35 - 10 = 25 guys inside two smaller ones. Inside the "math" circle M there are 20 guys, which means that they are in that part of the "biological" circle that is located outside the circle M, there are 25 - 20 = 5 biologists who do not attend the mathematical circle. The remaining biologists, there are 11 - 5 = = 6 people, are in the common part of the circles MB. Thus, 6 biologists are fond of mathematics.

Task 2..There are 38 people in the class. Of these, 16 play basketball, 17 play hockey, and 18 play football. They are fond of two sports - basketball and hockey - four, basketball and football - three, football and hockey - five. Three are not fond of basketball, hockey or football.

How many children are fond of three sports at the same time?

How many kids are into just one of these sports?

Solution. Let's use the Euler circles. Let the large circle represent all the students in the class, and the three smaller circles B, X, and F represent basketball, hockey, and football players, respectively. Then figure Z, the common part of circles B, X and F, depicts guys who are fond of three sports. From the consideration of Euler's circles it can be seen that 16 - (4 + z + 3) = 9 - z are engaged in only one kind of sport - basketball; hockey alone 17 - (4 + z + 5) = 8 - z;

football alone 18 - (3 + z + 5) = 10 - z.

We make an equation, using the fact that the class is divided into separate groups of children; The number of children in each group is circled in the figure with frames:

3 + (9 - z) + (8 - z) + (10 - z) + 4 + 3 + 5 + z = 38,

Thus, two guys are fond of all three sports.

Adding the numbers 9 - z, 8 - z and 10 - z, where z = 2, we find the number of guys who are fond of only one sport: 21 people.

Two guys are fond of all three kinds of human sports.

Fond of only one sport: 21 people.

Task 3. Some of the guys in our class like to go to the movies. It is known that 15 guys watched the film "Inhabited Island", 11 people - the film "Dandies", of which 6 watched both "Inhabited Island" and "Dandies". How many people watched only the movie "Dandies"?

We draw two sets in this way:

6 people who watched the films "Inhabited Island" and "Hipsters" are placed at the intersection of sets.

15 - 6 = 9 - people who watched only "Inhabited Island".

11 - 6 = 5 - people who watched only Stilyagi.

We get:

Answer. 5 people watched only "Dandies".

Task 4. Among schoolchildren of the sixth grade, a survey was conducted on their favorite cartoons. Three cartoons turned out to be the most popular: "Snow White and the Seven Dwarfs", "SpongeBob SquarePants", "The Wolf and the Calf". There are 38 people in the class. "Snow White and the Seven Dwarfs" was chosen by 21 students, among whom three also named "The Wolf and the Calf", six - "SpongeBob SquarePants", and one wrote all three cartoons. The cartoon "The Wolf and the Calf" was named by 13 children, among whom five chose two cartoons at once. How many people chose the SpongeBob SquarePants cartoon?

There are 3 sets in this problem, from the conditions of the problem it is clear that they all intersect with each other. We get this drawing:

Taking into account the condition that among the guys who named the cartoon “The Wolf and the Calf”, five chose two cartoons at once, we get:

21 - 3 - 6 - 1 = 11 - the guys chose only "Snow White and the Seven Dwarfs".

13 - 3 - 1 - 2 \u003d 7 - the guys watch only "The Wolf and the Calf."

We get:

38 - (11 + 3 + 1 + 6 + 2 + 7) = 8 - People only watch SpongeBob SquarePants.

We conclude that "SpongeBob SquarePants" was chosen by 8 + 2 + 1 + 6 = 17 people.

Answer. 17 people chose the cartoon "SpongeBob SquarePants".

Task 5. 35 customers came to the Mir Music store. Of these, 20 people bought a new disc by singer Maxim, 11 - Zemfira's disc, 10 people did not buy a single disc. How many people bought CDs for both Maxim and Zemfira?

We represent these sets on Euler circles.

Now let's calculate: There are 35 buyers inside the large circle, 35–10=25 buyers inside two smaller circles. According to the condition of the problem, 20 buyers bought a new disk by the singer Maxim, therefore, 25 - 20 = 5 buyers bought only Zemfira's disk. And the problem says that 11 buyers bought Zemfira's disk, which means 11 - 5 = 6 buyers bought both Maxim and Zemfira's disks:

Answer: 6 buyers bought both Maxim's and Zemfira's CDs.

Task 6. There were 26 magical spellbooks on the shelf. Of these, 4 were read by both Harry Potter and Ron. Hermione read 7 books that neither Harry Potter nor Ron read, and two books that Harry Potter read. read 11 books. How many books has Ron read?

Given the conditions of the problem, the drawing will be as follows:

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70 - (6 + 8 + 10 + 3 + 13 + 6 + 5) \u003d 19 - the guys do not sing, are not fond of sports, are not involved in the drama club. Only 5 people are engaged in sports.

Answer. 5 people are engaged only in sports.

Task 8. Of the 100 children who go to the children's health camp, 30 children can snowboard, 28 can skateboard, and 42 can roller skate. - 5, and on all three - 3. How many guys do not know how to ride a snowboard, or a skateboard, or rollerblading?

Three people own all three sports equipment, which means that in the common part of the circles we enter the number 3. 10 people can ride a skateboard and roller skates, and 3 of them also ride a snowboard. Therefore, only 10-3=7 guys can ride a skateboard and roller skates. Similarly, we get that 8-3=5 guys can ride only on a skateboard and snowboard, but only 5-3=2 people can ride on a snowboard and roller skates. We will enter these data in the relevant parts. Let us now determine how many people can ride only one sports equipment. 30 people know how to snowboard, but 5+3+2=10 of them also own other equipment, therefore, only 20 guys can snowboard. Similarly, we get that only 13 guys can ride a skateboard, and 30 guys can only skateboard. According to the condition of the problem, there are only 100 children. 20+13+30+5+7+2+3=80 - the guys know how to ride at least one sports equipment. Consequently, 20 people do not know how to ride a single sports equipment.

Answer. 20 people do not know how to ride a single sports equipment.

Leonhard Euler (1707-1783) - famous Swiss and Russian mathematician, member of the St. Petersburg Academy of Sciences, lived most of his life in Russia. The most famous in statistics, computer science and logic is the Euler circle (Euler-Venn diagram), used to denote the scope of concepts and sets of elements.

John Venn (1834-1923) - English philosopher and logician, co-inventor of the Euler-Venn diagram.

Compatible and incompatible concepts

In turn, each of the types of concepts has its own set of possible relations. For compatible concepts, these are the following:

identity (equivalence) of volumes;
intersection (partial coincidence) of volumes;
subordination (subordination).

For incompatible:

subordination (coordination);
opposite (contrararity);
contradiction (contradiction).

Schematically, the relationship between concepts in logic is usually denoted using Euler-Venn circles.

Equivalence relations

In this case, the terms mean the same subject. Accordingly, the volumes of these concepts are completely the same. For example:

A - Sigmund Freud;

B is the founder of psychoanalysis.

A - square;

B is an equilateral rectangle;

C is an equiangular rhombus.

Completely coinciding Euler circles are used for designation.

Intersection (partial match)

A - teacher;

B is a music lover.

As can be seen from this example, the volumes of concepts partially coincide: a certain group of teachers may turn out to be music lovers, and vice versa - there may be representatives of the teaching profession among music lovers. A similar attitude will be in the case when A is, for example, a "citizen", and B is a "driver".

Subordination (subordination)

For example:

A - tree;

B - pine.

The concept B will be subordinate to the concept A. Since the pine tree belongs to the trees, the concept A becomes in this example the subordinate, “absorbing” the scope of the concept B.

Subordination (coordination)

Attitude characterizes two or more concepts that exclude each other, but at the same time belong to a certain common generic circle. For example:

A - clarinet;

B - guitar;

C - violin;

D is a musical instrument.

Concepts A, B, C are not intersecting in relation to each other, however, they all belong to the category of musical instruments (concept D).

Opposite (contrary)

A - dwarf;

B is a giant.

Contradiction (contradiction)

A is a difficult task;

B is an easy task (not-A).

Thus, the ratio of the volumes of concepts in relation to each other is the key characteristic that defines the Euler circles.

Relationships between sets

The designation of the sets is carried out by A, B, C, D ... etc., the elements of the sets are lowercase: a, b, c, d ... etc. Examples of a set can be students in the same classroom, books standing on a certain shelf (or, for example, all the books in a particular library), pages in a diary, berries in a forest clearing, etc.

In turn, if a certain set does not contain a single element, then it is called empty and denoted by the sign Ø. For example, the set of intersection points is the set of solutions to the equation x 2 = -5.

Problem solving

Euler circles are actively used to solve a large number of problems. Examples in logic clearly demonstrate the connection with set theory. In this case, truth tables of concepts are used. For example, the circle labeled A represents the truth region. So the area outside the circle will represent false. To determine the diagram area for a logical operation, you should shade the areas that define the Euler circle in which its values for elements A and B will be true.

W - what do I like to do?

D - what do I get?

P - how can I make good money?

Let's depict this in the form of a diagram: in logic - the intersection relation):

The result will be those professions that will be at the intersection of all three circles.

Euler-Venn circles occupy a separate place in mathematics when calculating combinations and properties. The Euler circles of the set of elements are enclosed in the image of a rectangle denoting the universal set (U). Instead of circles, other closed figures can also be used, but the essence of this does not change. The figures intersect with each other, according to the conditions of the problem (in the most general case). Also, these figures should be labeled accordingly. The elements of the sets under consideration can be points located inside different segments of the diagram. Based on it, specific areas can be shaded, thereby designating the newly formed sets.

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Nowadays, a huge amount of information has been collected around us, it can be difficult to understand it. Therefore, many do not know that behind the name "Euler Circles" lies a practical and convenient method for solving various problems. Everyone has heard of them, but few can explain what they are. However, I believe that Euler Circles are useful both in everyday life and in science, so everyone should be able to use them. In this work, I have collected all the necessary information to understand what Euler Circles are and where it is convenient to use them.

Euler circles are a geometric diagram that can be used to visualize relationships between different sets and subsets. Such a scheme helps to find logical connections between phenomena and concepts; it was invented by Leonhard Euler and is used in mathematics and other scientific disciplines. The use of Euler circles simplifies reasoning and helps to get the answer faster and easier. (1),(2)

Euler circles are inextricably linked with the concept of a set. Therefore, in order to better understand what is depicted on the Euler circles, you need to know what a set is and what sets there are.

A set can be understood as a collection of any objects, called elements of a set. Sets can combine any objects with a common feature. For example, a set of students of gymnasium 11, students in grade 7 "B" constitute a separate set. Sets can be inanimate objects. For example, a lot of books written by some author. With the help of Euler circles, a set is denoted as an empty circle, and its elements are denoted by dots. (5)

Let's draw a lot of numbers. In the figure, the outline denotes a set, and the dots denote the elements of this set.

Sets are of three types:

final (for example - a set of numbers)

Infinite (for example - a set of numbers)

Empty (set of natural numbers

less than zero). (5)

A group of objects forming a set that is part of a larger set is depicted as a smaller circle drawn inside a larger circle and is called a subset. Such a relationship is formed between a large set of animals and its subset of flatworms. (5)

In those cases where two concepts coincide only partially, the relationship between such sets is depicted using two intersecting circles. Such an attitude is formed between a lot of students of the 7th "B" class and a lot of C students. Some elements of the set of students of the 7th "B" class also belong to the set of C students. (5)

When no object from one set can simultaneously belong to the second set, then the relationship between them is depicted by means of two circles drawn one outside the other. Such sets are the set of negative and the set of positive numbers. (5)

Euler circles were invented and named after Leonhard Euler (portrait on the left). He was a Swiss mathematician who made a significant contribution to the development of mathematics, as well as mechanics, physics, astronomy and a number of applied sciences. Euler was born in Switzerland, studied in Germany, but worked and died in Russia. This scientist is the author of 800 works. Leonhard Euler was born in 1707 in the family of a pastor. His father was a friend of the Bernoulli family. Euler showed early mathematical abilities. While studying at the gymnasium, the boy was enthusiastically engaged in mathematics, and later began to attend university lectures by Johann Bernoulli. On October 20, 1720, Leonhard Euler became an art student at the University of Basel. The gifted young man attracted the attention of Professor Johann Bernoulli. He gave the student mathematical articles for study, and also invited him to come to his house to jointly analyze the incomprehensible. At his teacher's house, Euler met and began to communicate with Bernoulli's sons, Daniil (portrait on the left) and Nikolai (portrait on the right), who also studied mathematics. (6)

Young Euler wrote several scientific papers. "Thesis in Physics on Sound" received a favorable review. At that time, the number of scientific vacancies in Switzerland was small. Therefore, the brothers Daniel and Nikolai Bernoulli left for Russia, where the Russian Academy of Sciences began to be created; they promised to work there for a position for Euler as well. At the beginning of the winter of 1726, Euler received a letter from St. Petersburg: on the recommendation of the Bernoulli brothers, he was invited to the post of adjunct in physiology with a salary of 200 rubles. Euler spent a lot of time in Russia, where he made a significant contribution to Russian science. Since 1731 he was elected an academician of the St. Petersburg Academy. He knew Russian well, and published essays and textbooks in Russian. (6)

Then Euler describes in detail his method for solving some problems using Euler circles. In 1741, Euler wrote "Letters on various physical and philosophical matters, to a certain German princess ..", where "Euler's circles" are mentioned. Euler wrote that "circles are very suitable for facilitating our reflections." (3)

Euler's method has received well-deserved recognition and popularity. And after him, many scientists used it in their work, and also modified it in their own way. Bernard Bolzano used the same method but with rectangular patterns. Thanks to the contribution of Venn, the method is even called Venn diagrams or even Euler-Venn. Euler circles have an applied purpose, that is, with their help, in practice, problems are solved for the union or intersection of sets in mathematics, logic, management, and more. (one)

Here are a few problems for solving which, it is convenient to use Euler circles:

Task 1.

The guys from one school were asked about their pets. 100 of them answered that they have a dog and/or a cat at home. 87 children had one dog and 63 children had one cat. How many kids have both a dog and a cat?

Solution:

To solve this problem without using Euler circles, you need to calculate how many dogs and cats the students had. To do this, add 87 and 63. 87+63=150 pets. There were only 100 students, and a fractional number of pets cannot be obtained. So if each student has 1 pet, there are still 50 extra. Therefore, 50 students have 2 pets. And since the problem states that none of the students has 2 cats or 2 dogs, this means that 50 students have both a cat and a dog.

But this method is long and only suitable for simple tasks. It is much more convenient to solve such a problem in terms of Euler circles.

The red circle will depict the set of dog owners, and the blue circle will represent the set of cat owners. There were 100 students in total. Those who have both a cat and a dog X. To find the number of students who have only a dog, you need to subtract X from 87. Since there are 100 students in total, we get:

X=50 students

Answer: 50 students have both a cat and a dog

Task 2.

Once the students were asked which of them loves mathematics, who likes the Russian language, and who likes physics. It turned out that out of 36 students, 2 do not like mathematics, nor Russian, nor physics. 25 students like mathematics, 11 students like Russian, 17 students like physics; both mathematics and Russian - 6; both mathematics and physics - 10; Russian language and physics - 4.

How many people like all three subjects?

Solution:

Let's draw 3 sets. The red set is those who love mathematics, the blue ones are those who love the Russian language, the green one is physics.

Now let's write the number of elements in the set. 6 people love both Russian and mathematics. Of these, X people also love physics. So, only math and Russian are loved by 6 people. Only mathematics and physics 10-X, only Russian and physics 4 people. 25 people love math. But X, 6-X, 10-X people also love other things. So, 25-(6-X)-(10-X)-X = 25-6+X-10+X -X=5+X people love only math. Only Russian is loved by 11-(6-X)-(4-X)-X= 11-10+2X-X=1+X students, only physics 17-(10-X)-(4-X)-X= 17-14+2X-X= 3+X.

Since 2 people do not like any of these items, then:

3+X+9+X+1+X+6-X+10-X+4-X+X=36-2

Answer: 1 person loves all three items

Task 3.

The table shows queries and the number of pages found by them for a certain segment of the Internet.

How many pages (in thousands) will be found for the query nature? (four)

Solution :

2,100,000 pages were found for a human query. 900 of them are also about nature. This means that there are 2100-900=200 thousand pages only about man, but only X-900 thousand about nature. We get that:

2100-900+X-900+900=3400

2100-900+X=3400

X=2200 thousand pages

Answer: 2,200,000 pages will be found for the query nature.

As you can see Euler circles are a useful and important discovery for mathematics in general and for each of us in particular. Euler circles are found not only in exams, but we also need them in everyday life. This is an interesting and necessary thing that should not be forgotten.

Literature:

https://www.tutoronline.ru/blog/krugi-jejlera

https://ru.wikipedia.org/wiki/%D0%9A%D1%80%D1%83%D0%B3%D0%B8_%D0%AD%D0%B9%D0%BB%D0%B5%D1 %80%D0%B0

http://sibac.info/shcoolconf/science/xvii/42485

http://www.jwy.narod.ru/logic/_04_eiler.html

https://ru.wikipedia.org/wiki/%D0%AD%D0%B9%D0%BB%D0%B5%D1%80,_%D0%9B%D0%B5%D0%BE%D0%BD %D0%B0%D1%80%D0%B4