Right angle, non-square angle

### 1.1. Knowledge to remember

#### 1.1.1. Getting to know the corner

*The two clock hands on each side form an angle*

#### 1.1.2. Right angle and non-square angle

Right angle of vertex O; Non-square angle of vertex P; Non-square angle vertex E;

edge OA, OB edge PM, PN edge EC, ED

#### 1.1.3. hey ke

The eke Use the eke to check the right angle

### 1.2. Solving textbook exercises

**Lesson 1:** a) Use êke to identify the right angle of the figure below and then mark the right angle (according to the pattern).

b) Use êke to draw:

– Right angle of vertex O ; edge OA, OB, (according to the pattern).

– Right angle of vertex M ; next to MC, MD.

**Solution guide**

- Place the vertices of the right angle in the vertices of the angle in the given figure, if the two sides of the right angle of the ruler coincide with the two sides of the angle being measured, it is a right angle.
- Mark a point, called the vertex of the angle. Place the square vertex of the keke coincident with the point just marked, draw two sides along the two right angles of the ruler.

a) Use an eke to check the right angle, then mark the right angle as follows:

b) Mark the point O, place the vertex of the right angle of the ruler coincident with the vertex O, draw the sides OA, OB along the two sides of the right angle.

Mark the point M, place the vertex of the right angle of the ruler coincident with the vertex M, draw the sides MC, MD along the two sides of the right angle.

**Lesson 2:** In the pictures below:

a) Name the vertex and the side of the right angle

b) Name vertices and sides of non-square angles.

**Solution guide**

- Use the checker to check whether the given angle is a right angle or a non-square angle.
- Read the vertex and two sides of each angle.

Using the checker, we have:

a) The right angles are :

+ Angle of vertex A, side AE, AD

+ Angle of vertex D, side DM, DN.

+ Angle of vertex G, side GX, GY

b) The non-square angles are:

+ Angle of vertex B, side BH, BG

+ Angle of vertex C, side CK, CI

+ Peak angle E, edge EP, EQ.

**Lesson 3:** In the quadrilateral MNPQ, which angle is a right angle? Which angle is a non-square angle?

**Solution guide**

In turn, place the vertex of the right angle of the eke into the four vertices M, N, P, Q of the quadrilateral, one side of the right angle of the ruler coincides with the side of the angle and then check those angles are right angles or not.

- Right Angle: The side of the remaining square of the ruler coincides with the other side of the angle.

- Non-Square Angle: The remaining right angle edge of the ruler does not coincide with the other side of the angle.

Using the checker we have:

The right angle is :

+ Angle of vertex M, side MN, MQ.

+ Angle of vertex Q, side QP, QM.

Non-square angles are:

+ Angle of vertex N, side NM, NP

+ Angle of vertex P, side PQ, PN.

**Lesson 4: **Circle the word in front of the correct answer

The number of right angles in the figure below is:

A. 1 B. 2 C. 3 D. 4

**Solution guide**

Using the eke check the angles of the given shape, count the number of right angles and then fill in the blanks.

The figure below has four right angles.

Circle the letter D.

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