What is a right angle. Right angle

Class: 2

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Lesson type: explanation of new material.

The place of the lesson in the structure on the topic: this topic is studied in the section “Tabular addition of single-digit numbers with the transition through ten”.

The purpose of the lesson: To introduce students to the concept of "right angle" and teach how to apply the knowledge gained in practice.

Lesson objectives:

1. Educational:

  • To introduce students to the concept of "right angle";
  • To form practical skills in determining the right angle with the help of a triangle and without it;
  • Continue work to improve the skill of mental counting within 100;

2. Developing:

  • Development of logical thinking, attention, memory, spatial imagination;
  • Development of creative skills and abilities on the topic for the successful completion of tasks;
  • Development of culture of speech and emotions of students.

3. Educational:

  • In order to solve the problems of moral education, to promote the education of humanity and collectivism, observation and curiosity, the development of cognitive activity, the formation of independent work skills;
  • In order to solve the problems of aesthetic education, to promote the development of a sense of beauty in students.

DURING THE CLASSES

I. Organizational moment.

Well check it out buddy
Are you ready to start the lesson?
Everything is in place
Is it all right
Pen, book and notebook?
Is everyone seated correctly?
Is everyone watching closely?
Everyone wants to receive
Only a rating of "5".

Guys, today we will again go on a journey through the Kingdom of Geometry.

3. Oral account.

“King Point and his daughter, Princess Straight, meet us at the gate. Before the king and princess introduce us to the inhabitants of their kingdom, they want to test you.

II. Verbal counting.

1) The game "Confused Caterpillar".

The caterpillar has lost the numbers, look at the rest, guess by what rule you can continue the series of numbers. (Children call the rule: these are even numbers; each subsequent number is 2 more than the previous one).

What numbers did the caterpillar lose? (2,4,6,8,10,12,14,16)

2) The game "Mathematical Basketball".

Basketball- a team sports game, the purpose of which is to throw the ball into a suspended basket with your hands.

Either of you will score a goal if the example solves correctly. (Children solve examples in a chain). 30 + 7 25 + 5 32 - 12 66 + 4 80 - 7 28 - 10 45 - 45 53 + 7 59 - 9 90 + 9

slide 5

Logic task

How many snouts do 15 piglets have? (15)

When a goose stands on two legs, it weighs 4 kg. How much will a goose weigh when it stands on one leg?

You have passed all tests. The king and princess are very pleased with you and are ready to introduce you to the inhabitants of the Geometry Kingdom!

(At a click, the gate leaves open.)

Guys, before you are the inhabitants of the kingdom "Geometry".

Look at the shapes in each frame. Which one is redundant? Why?

(Students name extra figures, justify their choice).

Divide all remaining shapes into two groups. How can I do that? (The remaining figures can be divided into two groups: lines and polygons.)

Name the types of lines and polygons that you know. (Lines: straight line, broken line, curve. Polygons: square, trapezium, rectangle, quadrilateral, pentagon, hexagon, polygon).

IV. Working on new material.

(Slide 8)

1) - The crossword puzzle will tell you the topic of the lesson. Crossword "Geometric".

1) A part of a line that has a beginning but no end. (Ray).

2) A geometric figure that has no corners. (Circle).

4) A geometric figure that has the shape of an elongated circle. (Oval).

The topic of our lesson is hidden vertically. Find her. (Corner). (click fly out geometric shapes).

Please state the topic of our lesson.

Guys, why are we going to study angles?

Do you think this knowledge will be useful to you?

(children's answers)

Corners surround us in everyday life. Give your examples of where you can find corners around us.

Guys, maybe someone knows what an angle is? (children's opinions are heard)

We will check the correctness of our formulation a little later.

People of what professions most often meet with angles? (constructor, engineer, designer, builder, architect, sailor, astronomer, architect, tailor, etc.)

Look at the pictures: connecting corner for pipes and stationery corner for papers; a carpenter's square and a drawing square; corner table and corner sofa.

Guys, and now the King and the Princess offer to play a little.

slide 10.

The game "The corner gave them a name."

Angle is an important figure. He helped to name many figures. Name the figures.

What do the names of the figures have in common? (that they have a square - a common part)

Why is the first part of words different everywhere? (because the number of corners is different)

Fizminutka 11-16 slides

Guys, now step back one cell from the red fields and put a point O. Draw two rays from this point.

On the board, draw a point O (4-5) in advance. Call 4-5 children to draw the rays on the board.

What shapes did we get? (corner)

See how different these angles are.

Guys, now collect the rule from the words.

Work in pairs.

(Conclusion: an angle is a geometric figure formed by two different rays

with a common beginning).

Guys, now look at the figure that I drew.

Is it a corner or not.

(Children say - no, once again we return to the rule, after that we conclude that this is also an angle - deployed)

Slide 19. (output by angle)

poster on chalkboard

Point O is the vertex of the corner. An angle can be called a single letter written near its top. Corner O. But there can be several corners that have the same vertex. How to be then? (On the sheet is a drawing of such angles)

Children's answers.

In such cases, if you call different angles with the same letter, it will not be clear which angle is in question. To prevent this from happening, one point can be marked on each side of the corner, put a letter near it and designate the corner with three letters, while always writing in the middle a letter denoting the top of the corner. Angle AOB. Rays AO and OB are the sides of the angle.

poster on chalkboard

Guys, you have different types of corners on your tables. Please find the same types of angles.

How will you search? (children's answers)

One person on my models is looking for the same angles.

Guys, look, numbers 6 and 7 coincided completely, but 1 and 5 did not. No. 5 more.

What can be the conclusion? After the children answer, a slide appears.

CONCLUSION: slide 21

  • Equal angles when superimposed coincide
  • If one angle is superimposed on another and they coincide, then these angles are equal

Making a model of a right angle.

It is not always convenient to determine the right angle by eye. To do this, use a ruler-gon.

What color is used to highlight an angle greater than a right angle? (blue).

Less direct? (Green).

What is the angle of the three proposed straight lines?

Why did you decide so? (The vertex and sides of the corner coincided with the right angle on the square ruler).

How to determine the type of angle?

  • To determine the type of angle, it is necessary to combine its vertex and side, respectively, with the vertex and side of a right angle on the square.

Each corner has its own name. An acute angle is an angle that is smaller than a right angle. An obtuse angle is an angle that is greater than a right angle.

(Plates with the names of the corners appear on the board)

My mother took the paper
And turned the corner
Angle like this in adults
It's called DIRECT.
If the angle is already ACUTE,
If wider, then - STUPID.

Guys, is it always possible to impose corners?

No. (If drawn in a notebook ...)

To do this, there is a protractor, with which angles are measured. Angles are measured in degrees. Look at the types of transporters.

Very often we can observe the angles on the clock. The corners form hour hands.

Textbook work.

Exercise: Using the right angle model, find the right angles and write down their numbers. (Children complete the task on their own, then one student calls his answer, everyone checks the work).

With the help of a square, it is convenient not only to determine right angles, but the main thing is to build them. Let's build a right angle, everyone will call it one or three letters.

Slide 27-29 (The teacher is on the blackboard, and the children in the notebooks build a right angle. Peer review is performed in pairs).

I am ACUTE - I want to draw,
Now I will take and draw.
I lead two straight lines from a point,
Like two beams
And we see an ACUTE ANGLE,
like the edge of a sword.

And for the STUPID ANGLE
We repeat everything again:
We draw two straight lines from a point,
But let's spread them out.
Look at my drawing
He's like scissors inside
If there are two rings
We'll push it to the end.

Practical work to consolidate what has been learned.

You have wire on your desks. Make a right angle out of it and check with a square, then make it sharp and blunt.

7. The result of the lesson.

Tell me in a diagram about what today's math lesson gave you?

8. Homework.

Each angle, depending on its size, has its own name:

Angle view Size in degrees Example
Spicy Less than 90°
Straight Equal to 90°.

In the drawing, a right angle is usually denoted by a symbol drawn from one side of the angle to the other.
Blunt Greater than 90° but less than 180°
deployed Equals 180°

A straight angle is equal to the sum of two right angles, and a right angle is half the straight angle.
Convex More than 180° but less than 360°
Full Equals 360°

The two corners are called related, if they have one side in common, and the other two sides form a straight line:

corners MOP And pon adjacent since the beam OP- the common side, and the other two sides - OM And ON make up a straight line.

The common side of adjacent angles is called oblique to straight, on which the other two sides lie, only if the adjacent angles are not equal to each other. If adjacent angles are equal, then their common side will be perpendicular.

The sum of adjacent angles is 180°.

The two corners are called vertical, if the sides of one angle complement to straight lines the sides of another angle:

Angles 1 and 3, as well as angles 2 and 4, are vertical.

Vertical angles are equal.

Let's prove that the vertical angles are equal:

The sum of ∠1 and ∠2 is a straight angle. And the sum of ∠3 and ∠2 is a straight angle. So these two sums are equal:

∠1 + ∠2 = ∠3 + ∠2.

In this equality, on the left and on the right there is the same term - ∠2. Equality is not violated if this term on the left and on the right is omitted. Then we get.

DIRECT, oh, oh; straight, straight, straight, straight and straight. Explanatory dictionary of Ozhegov. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 ... Explanatory dictionary of Ozhegov

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