"Position-like Figures" PPT courseware

Description

"Position-like Figures" PPT courseware

Observe and think

In the following figures, the quadrilateral ABCD and the quadrilateral A′B′C′D′ in each figure are similar figures. Observe these five figures respectively, and you will find that the lines connecting the corresponding points of the two quadrilaterals in each figure are: What characteristics?

Clarify new knowledge

If the straight lines of each set of corresponding points of two similar figures intersect at one point, then the two figures are called similarity figures, and the intersection point is called the similarity center. At this time, the similarity ratio of the two similar figures is also called their location. Similar.

Discuss Observe the five pictures in the figure below and answer the following questions:

(1) In each figure, what is the positional relationship between the position-like center of the position-like figure and the two figures?

The position is different, and the position and center are different.

(2) In each figure, pick any pair of corresponding points and measure the distance between the two points from the center of the similarity. What is the relationship between their ratio and the ratio of the similarity? Try another pair of corresponding points.

equal.

Analysis of typical cases

As shown in the figure, D and E are points on AB and AC respectively.

(1) If DE∥BC, then are ΔADE and ΔABC similar figures? Why?

Solution: (1) ΔADE and ΔABC are similar figures. The reason is:

Because DE∥BC, so ∠ADE and =∠B, ∠AED =∠C. So ΔADE∽ ΔABC.

And because point A is the common point of ΔADE and ΔABC, point D and point B are corresponding points, point E and point C are corresponding points, and straight lines BD and CE intersect at point A, so ΔADE and ΔABC are similar in position. graphics.

(2) If ΔADE and ΔABC are similar figures, then is DE∥BC? Why?

Solution: (2) DE∥BC. The reason is:

ΔADE and ΔABC are similar figures, ΔADE∽ ΔABC, ∠ADE=∠B, DE∥BC.

Class summary

What did you gain from studying this class?

1. If the straight lines of each set of corresponding points of two similar figures intersect at one point, then such two figures are called similarity figures, and this intersection point is called the similarity center. At this time, the similarity ratio of the two similar figures is also called their similarity ratio. The bit-like ratio.

2. The corresponding points of the similarity figure and the similarity center are on the same straight line, and the ratio of their distances from the similarity center is equal to the similarity ratio.

3. The corresponding line segments in the similarity figure that do not pass through the center of the similarity are parallel.

Keywords: teaching courseware of position-like figures, download the ninth-grade mathematics PPT courseware of Hebei Education Edition, download the ninth-grade mathematics slide courseware, download the PPT courseware of position-like figures, .PPT format;

For more information about the PPT courseware of "Simultaneous Figures", please click the "Simultaneous Figures" ppt tab.

File Info

Update Time: 2024-07-07

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

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