"Comparison of Line Segment Length" PPT Courseware 2

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"Comparison of Line Segment Length" PPT Courseware 2

Test your eyesight

Which one is longer, line segment AB or line segment CD?

How many methods do you have to compare the lengths of two line segments?

1. You can use a ruler to measure the lengths of two line segments, and then compare them. ——Measurement method.

2. You can compare two line segments by superimposing them together. ——Superposition method.

Overlay method

Summary: The measurement method is used to compare sizes from the aspect of numbers, while the superposition method is used to compare sizes from the aspect of shape.

Line segment AB is shorter than line segment A1B1, that is, AB

Line segment AB is longer than line segment A2B2, that is, AB>A2B2

Line segment AB is the same length as line segment A3B3, that is, AB=A3B3

Example 1: As shown in the figure, given the line segment a, use a compass and a ruler to draw the line segment AB so that AB=a

1. Draw ray AC;

2. Intercept AB=a on ray AC

Draw an arc with point A as the center and a as the radius. The intersection line AC is at point B.

Line segment AB is the line segment to be drawn.

Art style:

① Make ray AB;

② Use a compass to measure the length of the known line segment (recorded as a);

③ Intercept AC = a on ray AB.

Notice:

The problem of drawing with ruler and compass,

1. A ruler can only be used to draw lines, not distances.

2. Drawing with ruler and compass requires making graphics, explaining the results, and retaining traces of the drawing.

The little rabbit wants to get from point A to point B.

⑴Which of the three routes in the picture is relatively close?

⑵Is there the shortest route?

Of all the lines connecting two points, the line segment is the shortest.

The distance between two points is the length of the line segment connecting the two points.

Ability Challenge

1. As shown in the figure, there is a fly and a spider at the two farthest vertices of the cube.

(1) Which is the shortest path that a spider can take to crawl to a fly? Give your reasons?

(2) If a spider wants to crawl along the edge to reach the fly, how many shortest routes are there?

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"Comparison of Line Segment Lengths" PPT Courseware Review Old Knowledge The essential difference between line segments, rays, and straight lines is that _____ has no endpoints, _____ has only one endpoint, and _____ has two endpoints. The basic property of a straight line is: there is only one straight line passing through two points. Line segments, rays...

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Update Time: 2024-11-16

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

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