"Orthographic Projection" Projection and View PPT

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"Orthographic Projection" Projection and View PPT

Part One: Learning Objectives

Master the rules of orthographic projection of line segments and plane figures; taking the cube as an example, master the shape and size of the orthographic projection formed at two different positions with the projection surface;

Master the orthographic projection of several basic geometric shapes.

Orthographic projection PPT, part 2: independent learning

Independent learning task: Read pages 88-91 of the textbook and master the following key points.

1. The rules of orthographic projection of line segments and plane figures; the shape and size of the orthographic projection formed at two different positions of the projection surface;

2. Orthographic projections of several basic geometries.

Independent learning feedback

1.The orthographic projection of a right triangle may be ______________.

2. We know that the projection formed by parallel light rays is called parallel projection. When the parallel light ray and the projection surface _______, this kind of projection is called orthographic projection.

3. The projection formed by sunlight is __________, and the projection formed by the light emitted by flashlights and light bulbs is __________.

4. The seats in large auditoriums are arranged in a ladder shape. The reason for this arrangement is ______________.

Orthographic projection PPT, the third part: new knowledge explanation

The concept and properties of orthographic projection

Observe and think

The figure shows that a triangle ruler forms a projection when illuminated by light. What is the difference between the projection lines in Figure (1) and Figures (2) and (3)? What is the difference between the positional relationship between the projection line and the projection surface in Figures (2) (3)?

In Figure (2), the projection line illuminates the projection surface obliquely;

In Figure (3), the projection line illuminates the projection surface vertically (that is, the projection line is facing the projection surface). We also call this situation that the projection line is perpendicular to the projection surface.

Like Figure (3), the projection produced by the projection line perpendicular to the projection surface is called orthographic projection.

collaborative inquiry

As shown in the figure, place a straight thin wire (recorded as line segment AB) in three different positions;

(1) The wire is parallel to the projection surface;

(2) The wire is inclined to the projection surface;

(3) The wire is perpendicular to the projection surface (the wire does not necessarily have to intersect with the projection surface).

What is the shape of the orthographic projection of the wire in the three situations?

in conclusion

Through observation, we can find:

(1) When the line segment AB is parallel to the projection plane α, its orthographic projection is the line segment A1B1, and the size relationship between the line segment and its projection is AB_____A1B1;

(2) When line segment AB is inclined to the projection plane α, its orthographic projection is line segment A2B2, and the size relationship between the line segment and its projection is AB______A2B2;

(3) When line segment AB is perpendicular to the projection plane α, its orthographic projection is a ________.

Observe and think

As shown in the figure, place a square piece of cardboard P (denoted as square ABCD) in three different positions:

(1) The cardboard is parallel to the projection surface; (2) The cardboard is inclined to the projection surface;

(3) The cardboard is perpendicular to the projection surface.

What is the shape of the orthographic projection of the cardboard in the three situations?

in conclusion

Through observation and measurement, we know that:

(1) When the cardboard P is parallel to the projection plane β, the orthographic projection of P and the _______________ of P;

(2) When the cardboard P is tilted to the projection plane β, the orthographic projection of P and the _______________ of P;

(3) When the cardboard P is perpendicular to the projection plane β, the orthographic projection of P becomes _______________.

In conclusion

When a certain surface of an object is parallel to the projection surface, the orthographic projection of this surface has exactly the same shape and size as this surface.

Draw orthographic projection of geometry

Example: Draw the orthographic projection of the cube placed as shown in the figure on the projection plane P.

(1) One face ABCD of the cube is parallel to the projection plane P

(2) One surface ABCD of the cube is inclined to the projection surface P, the upper bottom surface ADEF is perpendicular to the projection surface P, and the diagonal AE of the upper bottom surface is perpendicular to the projection surface P.

Analysis: (1) When the cube is in the position shown in the figure, one face ABCD of the cube and the other face opposite to it are parallel to the projection surface. The orthographic projection of these two faces is exactly the same shape and size as one face of the cube. Square A´B´C´D´. The four sides of the square A´B´C´D´ are the projections of the remaining four faces of the cube (these faces are perpendicular to the projection plane). Therefore, the orthographic projection of the cube is a square.

(2) When the cube is in the position as shown in the figure, its surface ABCD and surface ABGF are inclined to the projection surface, and their projections are rectangles A´B´C´D´ and A´B´G´F´ respectively; the rest of the cube The projections of the two side surfaces are also the above-mentioned rectangles; the projections of the upper and lower bottom surfaces are line segments D´F´ and C´G´ respectively. Therefore, the projection of the cube is the rectangle F´G´C´D´, where the line segment A´B´ bisects the rectangle.

Orthographic projection PPT, part 4: in-class testing

1. The orthographic projection of the ball is ( )

A. Circular surface B. Elliptical surface C. Point D. Ring.

2. The length of the wooden stick is 1.2m, then the length of its orthographic projection is certain ( )

A. Greater than 1.2m B. Less than 1.2m

C. Equal to 1.2m D. Less than or equal to 1.2m

3． When Xiao Ming was practicing parallel bars on the playground, he found the shadow of the two horizontal bars on the ground during the practice ( )

A. Intersect B. Parallel C. Perpendicular D. Unable to determine

Orthographic projection PPT, Part 5: Apply what you have learned

1. In the picture below, the mouth of the water cup is parallel to the projection surface. The direction of the projection line is as shown by the arrow. Its orthographic projection is ( )

2. The picture on the right below shows the orthographic projection of a regular pentagonal prism when light shines from top to bottom. Can you point out what the orthographic projections of each face of the regular pentagonal prism are at this time?

Answer: The orthographic projections of each face of a regular pentagon are the sides of the regular pentagon.

Orthographic projection PPT, part 6: Class summary

orthographic projection

The concept and properties of orthographic projection

orthographic projection of plane graphics

orthographic projection of geometry

Keywords: Free download of PPT courseware for mathematics in the second volume of the ninth grade of the People's Education Press, download of orthographic projection PPT, download of projection and view PPT, .PPT format;

For more information about the "Projection and View Orthographic Projection" PPT courseware, please click on the Projection and View PPT Orthographic Projection PPT tab.

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Update Time: 2024-11-20

This template belongs to Mathematics courseware People's Education Press Ninth Grade Mathematics Volume 2 industry PPT template

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