"Parallel Projection" PPT courseware

Description

"Parallel Projection" PPT courseware

learning target

1. Explore the formation of shadows of objects, identify the shadows of objects according to the direction of light, and initially experience the mutual transformation between objects and shadows under parallel projection;

2. Through accumulation of activities, understand that the size and direction of the shadows formed by objects under sunlight are different at different times.

Observe and think

Do you know what the relationship between objects and shadows is?

When an object is illuminated by sunlight or light, it will form a shadow on the ground, walls, etc. The shadow is closely related to the shape of the object.

When an object is illuminated by light, it will leave its shadow on the ground or a strong surface. This phenomenon is called projection.

The sun's rays can be regarded as parallel. When such rays shine on an object, the projection formed is called parallel projection. The light is the projection line, and the ground or strong surface is the projection surface.

Explore new knowledge

Self-study textbook P165-P166 Do it

1. Under parallel projection, what is the projection of point A in the projection plane H?

2. What is the shape of the shadow of a suspended bamboo pole on the ground? Changing the angle between the bamboo pole and the ground, what happens to their shadows?

Parallel projection properties:

When the line segment is parallel to the projection surface, the projection of the line segment is a ______, both ______ and ______; when the line segment is inclined to the projection surface, the projection of the line segment and the line segment ______ are not necessarily equal; when the endpoint of the line segment is at When on the same ray, the projection of the line segment is a ______.

Expand and extend

Self-study textbook P166 Do it

If the sun shines obliquely on the ground, what shape will be the shadow of a rectangular piece of paper on the ground?

Summarize:

Regardless of the position of the rectangular piece of paper, the shadow in the sunlight is always ______. In particular, it may be ______, but it will not be ______.

Consolidation exercises

Generally, the projections of two objects standing upright on the ground in the sun are either parallel or on the same straight line. The two objects, their parallel projections and the projection line passing through the top of the object form a right triangle respectively. These two triangles resemblance.

The flagpole stands upright at position A, and its parallel projection is as shown in the figure.

(1) Please draw the projection of Xiao Ming when he is standing at B (represented by a line segment). And explain why you drew it this way.

(2) If Xiao Ming is standing at C, please draw his projection (represented by a line segment), and compare the length of the two projections of Xiao Ming standing at B and C.

(3) What is the relationship between the height of the flagpole and the ratio of its projected length and the ratio of Xiao Ming’s height to his projected length? Why?

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"Parallel Projection" PPT courseware 2:

"Parallel Projection" PPT courseware 2 In parallel projection, when the projection line is perpendicular to the projection plane, the projection of the geometry in the projection plane is called orthographic projection. Explore new knowledge. Place a line segment AB in three different positions: (1) The line segment is parallel to the projection surface. (2) The line segment is inclined..

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Update Time: 2024-09-29

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

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