"The Rotation of Graphics" PPT courseware

Description

"The Rotation of Graphics" PPT courseware

Perceive rotation

Perceive the phenomenon of rotation in life, observe and think about whether the shape, size, and position of objects change during the rotation process?

Observe and think

Think: What is rotation? What does the position of the rotated figure depend on?

Summary and induction

In the same plane, a figure is rotated by a certain angle in a certain direction (counterclockwise or clockwise) around a fixed point. This change in the figure is called rotation. This fixed point O is called the center of rotation, and the angle of rotation is called the angle of rotation. Rotation only changes the _______ of the figure but does not change the _______ of the figure.

The position of the rotated graphic is determined by ___________, ___________ and ___________

Explore and discover

A figure and the figure obtained by rotating it

The distance between the corresponding point and the center of rotation is equal;

The angles formed by the two sets of corresponding points with the line connecting the rotation centers are equal to each other.

Experience with your heart

1. Rotate �ABC 30° counterclockwise around point O. Can you point out the center of rotation, direction and angle of rotation? Can you point out the corresponding points of points A, B, and C respectively?

2. What factors determine the position of turning �ABC to �A`B`C`?

Read the experiment and inquiry on page 174 of the textbook and complete the following questions

1. Rotate �ABC to the position of �A`B`C`. Can you point out the center of rotation, direction of rotation and angle of rotation? Can you point out the corresponding points of points A, B, and C respectively?

2. Observing the above, what factors do you find determine the rotation of �ABC to the position of �A`B`C`?

Practice in class

1. As shown in Figure 4, △ABC can overlap with △ADE after rotating a certain angle around point A. If the area of ​​△ABC is 12cm2, then the area of ​​△ADE is ( )

2. As shown in Figure 5, △ABC is an equilateral triangle, D is the point on the side BC, ∠BAD=15°, △ABD reaches the position of △ACE after rotation, then the degree of the rotation angle is .

3. As shown in the figure on the right, △ABC takes point A as the rotation center and rotates 600 counterclockwise to obtain △AB‘C’, then △ABB‘ is a ________ triangle.

4. (2013 Nanchang) As shown in the figure, rotate △ABC counterclockwise around point A by a certain angle to get △ADE. If ∠CAE=65°, ∠E=70°, and AD⊥BC, the degree of ∠BAC is ()

Simple rotation drawing

Example 1 Rotate point A 60˚ clockwise around point O.

practice:

1. Draw a circle with point O as the center and length OA as the radius;

2. Connect OA, use a protractor or a triangle (special angles only) to make ∠AOB, and intersect the circle at point B;

3. Point B is the required operation.

Example 2 Rotate line segment AB 60˚ clockwise around point O.

practice:

1. Rotate point A 60˚ clockwise around point O to get point C;

2. Rotate point B 60˚ clockwise around point O to obtain point D;

3. Connect CD, then the line segment CD is the desired construction.

Example 3 As shown in the figure, after △ABC is rotated around point C, the corresponding point of vertex A is point D. Try to determine the position of the corresponding point of vertex B and the rotated triangle.

Method one:

1. Connect CD;

2. Taking CB as one side, construct ∠BCE so that ∠BCE=∠ACD;

3. Intercept CE on ray CB so that CE=CB;

4. Connect DE, then △DEC is the required solution.

Class review: What was the main thing learned in this class?

The concept of rotation:

In a plane, rotating a figure by a certain angle in a certain direction around a fixed point is called rotation.

Properties of rotation:

1. Rotation does not change the size and shape of the graphic.

2. The angle formed by the line connecting any pair of corresponding points and the center of rotation is the rotation angle, and the rotation angles are equal.

3. The distance between the corresponding point and the center of rotation is equal

Keywords: rotation teaching courseware of graphics, Qingdao edition eighth grade mathematics volume 2 mathematics PPT courseware download, eighth grade mathematics slide courseware download, rotation of graphics PPT courseware download, .PPT format;

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Update Time: 2024-11-22

This template belongs to Mathematics courseware Qingdao Edition Eighth Grade Mathematics Volume 2 industry PPT template

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