"The Size of the Angle" PPT courseware

Description

"The Size of the Angle" PPT courseware

Can you trace the open corners of the fan in the picture?

If you were asked to classify these four corners, how would you classify them?

Tell us what you think.

If divided according to the size of the angle, angles can be divided into the following categories:

Classification of angles

Acute angle 0°＜∠a＜90°

Right angle ∠a=90°

Obtuse angle 90°＜∠a＜180°

Straight angle ∠a=180°

Circumferential angle ∠a=360°

Tip: A right angle can be represented by Rt∠. When drawing, you often add "" at the vertex of the right angle to indicate that the angle is a right angle.

discussion one discussion

Try to compare the lengths of line segments AB and CD.

(1) Measurement method

Use a scale to measure that line segment AB is 4cm long and line segment CD is 4.5cm long, so line segment AB is shorter than line segment CD.

(Recorded as AB＜CD or CD＞AB)

(2) Duplicate law

"Move" a line segment so that one endpoint coincides with an endpoint of another line segment, and the other endpoints of both line segments are on the same ray.

Do it, compare it

1. Ask the students to take out the triangles they have made and compare the sizes of each angle of the triangle with their classmates.

2. Which of the following statements is correct ( )

A. The longer the sides of the angle, the larger the angle.

B. The size of the angle has nothing to do with the length of the side.

C. The size of the angle is related to the position of the vertex.

D. The size of the angle depends on the direction of rotation of the initial side.

Warm reminder: The size of the angle is only related to the size of the opening and has nothing to do with the length of the side; and please pay attention to the difference between the symbol of the angle and the less than sign and greater than sign when writing.

Solve the following questions based on the diagram on the right

(1) Find the right angles, acute angles and obtuse angles in the figure

(2) Compare the sizes of ∠AOB, ∠AOC, ∠AOD, and ∠AOE

Solution: (2) It can be seen from the picture on the right:

∠ AOB <∠ AOC < ∠ AOD < ∠ AOE

Solution: (1) The right angles in the figure are ∠AOC, ∠BOD, ∠COE;

Acute angles include ∠ AOB, ∠ BOC, ∠ COD, ∠ DOE;

Obtuse angles include ∠ AOD and ∠ BOE.

Practice and Demonstration

(1) Make ray O′A′:

(2) Take point O as the center of the circle, draw an arc with the length of OC as the radius, intersect OA at point C, and intersect OB at point D;

(3) Take point O′ as the center of the circle, draw an arc with the length of OC as the radius, and intersect O′ A′ at point C′;

(4) Take point C′ as the center of the circle, draw an arc with the CD length as the radius, and intersect the previous arc at point D′;

(5) Draw ray O ′ B ′ through point D ′.

So ∠ A ′ O ′ B ′ is the angle required.

discussion one discussion

⑴Is this the correct approach? How should you test it?

⑵Measure it,

⑶From the drawing ∠AOB, what do you think is the key to determining the size of ∠AOB?

⑷If there is another point C outside angle O, can you use a ruler to calculate ∠COD and make ∠AOB=∠COD?

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For more information about the "Size of Angle" PPT courseware, please click the "Size of Angle ppt" tab.

"Recognizing angles, comparing angle sizes, drawing angles" PPT courseware for preliminary understanding of angles:

1. Connect with life and reveal the subject (1) Find the corners in life (2) Reveal the subject 2. Understand the corners and the names of their parts 1. Point to where there are corners. 2. Which of the following figures are angles and which are not angles? 3. Comparing the sizes of the angles, I found that the two sides of the angle are wider...

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Update Time: 2024-11-21

This template belongs to Mathematics courseware Hebei Education Edition Seventh Grade Mathematics Volume 1 industry PPT template

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