In this lesson, we will learn how to use a compass and a ruler

to construct a line segment of a certain length.

to copy a line segment.

Construct a Line Segment

Example:

Construct a line segment with length 6 cm.

Solution:

Step 1 : Use a ruler to draw a straight line that is slightly longer than 6 cm. Mark the starting point (P) near the beginning of the line.

Step 2 : Stretch the 2 arms of the compasses on the ruler until the distance between the sharp end and the pencil end is 6 cm apart.

Step 3 : Put the compasses on the line with the sharp end at point P and mark an arc on the line using the pencil end.

Step 4: Remove the compasses and mark the point where the arc meets the line as point Q.

Note : While it may be easier to construct the line segment by simply marking off 6 cm with a ruler, this technique of using compasses is essential for other construction lessons.

The following video shows how to construct a line segment of a given length, on a given ray.

Copy a Line Segment

The following video shows how to copy a line segment using only a compass and straightedge.

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