Similar PPT courseware for the graphics "Proportional Line Segment" 3

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Similar PPT courseware for the graphics "Proportional Line Segment" 3

Knowledge review

If the ratio of two numbers is equal to the ratio of two other numbers, the four numbers are said to be proportional.

We proportion the four numbers a, b, c, and d,

a and d are called proportional external terms, b and c are called proportional internal terms,

1. Assume line segment AB=2cm, AC=4cm, the length ratio of the two line segments is 2:4=1/2

2. Suppose line segment AB=200cm, AC=4m, the length ratio of the two line segments is 200:400=1/2

The ratio of the lengths of two line segments is called the ratio of the two line segments

There are two ways to determine whether four line segments are proportional:

(1) Arrange the four line segments according to size and determine whether the ratio of the first two line segments is equal to the ratio of the last two line segments.

(2) Check whether the product of two line segments is equal to the product of the other two line segments.

1. Given the line segment a=2cm, b=4.1cm, c=4cm, d=8.2cm, which of the following options is correct? ( )

A. d, b, a, c are proportional line segments B. a, d, b, c are proportional line segments

C. a, c, b, d are proportional line segments D. a, d, c, b are proportional line segments

2.The length of the following groups of line segments is proportional to ( )

A.2cm,3cm,4cm,1cm B.1.5cm,2.5cm,6.5cm,4.5cm

C.1.1cm,2.2cm,3.3cm,4.4cm D.1cm,2cm,2cm,4cm

Example 2 As shown in the figure, in the right triangle ABC, CD is the altitude line on the hypotenuse AB. Please find a set of proportional line segments and explain the reason.

Analysis: (1) According to the basic properties of proportion, what method can be used to determine whether four line segments are proportional?

(See if the product of two line segments is equal to the product of the other two line segments)

(2) Among the known conditions is the height of a triangle. What knowledge can we usually associate the height with?

(3) Based on the area formula of a triangle, what kind of equation can you get? What proportional expression can be written based on the obtained equation.

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For more information about the PPT courseware "Similar Proportional Line Segments of Graphs", please click the "Similar Proportional Line Segments of Graphs" ppt tag.

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Update Time: 2024-10-02

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

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