"Magnification and reduction of graphics" similar graphics PPT courseware

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"Magnification and reduction of graphics" similar graphics PPT courseware

Review and Reflection

What are similar polygons?

What is the similarity ratio of similar polygons?

What are some ways to determine if two triangles are similar?

Do you still remember the method of using rubber bands to enlarge graphics on P104 in the third section of this chapter?

Do you still remember how to make fish longer and fatter in the "Changing Fish" lesson last semester? How to enlarge the fish?

Can you use these methods to scale up and down a known polygon? Is there a better way?

Special cases of similar figures

The following set of pictures are graphics with the same shape. Take point A on picture ①. Does the line connecting it to the corresponding point B on another picture (such as picture ②) pass through the center of lens P? Change the picture Try other places, are there any similar conclusions?

If two figures are not only similar, but also the straight lines of each set of corresponding points pass through the same point, then such two figures are called similarity figures, and this point is called the similarity center. The similarity ratio at this time is also called the similarity ratio. .

Knowledge comes from enlightenment

The three sides of △ABC can be reduced to 1/2 of their original size as follows:

As shown in the figure, take any point O, connect AO, BO, CO, and take their midpoints D, E, F;

The three sides of △DEF are 1/2 of the corresponding three sides of △ABC.

In fact, △ABC and △DEF are similar figures.

Do it:

Draw any triangle and try it yourself using the above method.

Think about it and do it

If it's the above example, do you have any other methods?

What if we take points A′, B′, C′, D′, E′, F′, G′ on the ray PA, PB, PC, PD, PE, PF, PG in sequence?

The result is an upward arrow.

The new shape is similar to the original shape, and the similarity ratio is 2:1.

Is the following statement correct? Why?

Take points D and E on the sides AB and AC of △ABC respectively, so that DE∥BC, then △ADE is the reduced figure of △ABC;

Take points D and E on the extension lines of sides AB and AC of △ABC respectively, so that DE∥BC, then △ADE is the enlarged figure of △ABC;

Take points D and E on the reverse extension lines of sides AB and AC of △ABC respectively, so that DE∥BC, then △ADE is the reduced figure of △ABC;

Summary and expansion

Similar polygon:

If two figures are not only similar, but also the straight lines of each set of corresponding vertices pass through the same point, then such two figures are called similarity figures, and this point is called the similarity center. The similarity ratio at this time is also called the similarity ratio. .

The property of the similarity ratio: the ratio of the distance between any pair of corresponding points on the similarity graph and the similarity center is equal to the similarity ratio

How to make positional images (enlargement and reduction; forward and inverted images).

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For more information about the PPT courseware "Enlarging and Reducing Similar Figures and Figures", please click the Enlargement and Reduction of Similar Figures PPT Figures ppt tab.

"Magnification and reduction of graphics" similar graphics PPT courseware 3:

"Amplification and Reduction of Figures" Similar Figures PPT Courseware 3 Learning Objectives 1. Understand the similarity figures and related concepts, and understand that the ratio of the distance between any pair of corresponding points on the similarity figures is equal to the similarity ratio. 2. Be able to Use the method of positioning a figure to place a figure...

"Magnification and reduction of graphics" similar graphics PPT courseware 2:

"Enlarging and Reducing Figures" Similar Figures PPT Courseware 2 Review and Thinking What are similar polygons? What is the similarity ratio of similar polygons? What are some ways to determine if two triangles are similar? Do you still remember the method of using rubber bands to enlarge graphics on page 116 of the third section of this chapter?

"Magnification and reduction of graphics" Transformation and position determination of graphics PPT courseware 3:

"Enlarging and Reducing Graphics" Transformation and Position Determination of Graphics PPT Courseware 3 These three sets of pictures have the same shape but different sizes. Like this: the shape is the same, but the figure becomes larger, which is called enlargement of the figure. The shape is the same, but the figure becomes smaller, which is called the reduction of the figure. The left picture is long (..

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Update Time: 2024-06-25

This template belongs to Mathematics courseware Beijing Normal University eighth grade mathematics volume 2 industry PPT template

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