Similar PPT courseware 3 of the graphic "Parallel lines are proportional to their segments"

Description

Similar PPT courseware 3 of the graphic "Parallel lines are proportional to their segments"

review review

1. The concept of proportional line segments:

Among the four line segments a, b, c, d, if a:b=c:d, then these four line segments a, b, c, d are called proportional line segments, or proportional line segments for short.

2. Basic properties of proportion

If a:b =c:d, then ad =bc.

If ad =bc, then a:b =c:d.

If a:b =c:d, then (a-b):b =(c-d):d; (a+b):b =(c+d):d.

inference

A straight line parallel to one side of a triangle intersects the other two sides (or the extension lines of both sides), and the corresponding line segments intercepted are proportional.

Class summary

1. The proportional theorem of line segments of parallel lines:

(1) Two straight lines are intercepted by a set of parallel lines, and the corresponding line segments obtained are proportional (the key is to be able to skillfully find the corresponding line segments)

(2) A straight line parallel to one side of a triangle intersects the other two sides (or the extension lines of both sides), and the corresponding line segments intercepted are proportional.

2. Be familiar with several basic graphics of this theorem

Expand and extend

As shown in the figure, in △ABC, DE//BC, DF//AC, AE=4, EC=2, BC=8. Find the lengths of BF and CF.

Analysis: Use the corollary of the proportional theorem of parallel line segments to list the proportional formulas to solve them.

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For more information about the PPT courseware "Similarities of Proportional Figures of Parallel Lines Divided into Line Segments", please click the Similar ppt tag of Proportional Figures of Parallel Lines Divided into Line Segments.

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Update Time: 2024-10-04

This template belongs to Mathematics courseware Beijing Normal University Ninth Grade First Volume Mathematics industry PPT template

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