Copying a line segment
Geometry construction using a compass and straightedge

This page shows how to copy a line segment with compass and straightedge or ruler. Given a line segment, this shows how to make another segment of the same length.

Printable step-by-step instructions

The above animation is available as a printable step-by-step instruction sheet, which can be used for making handouts or when a computer is not available.

Proof

The proof of this construction is trivial. Refer to the figure above in step 8.

  Argument Reason
1 All points along the the arc S are the same distance from R R is the center of the arc. See Arc definition
2 This distance is equal to the length of segment PQ The arc was drawn with that compass width
3 RS is congruent to PQ S is a point on the arc. See (1).

  - Q.E.D

Try it yourself

Click here for a printable worksheet containing two line segment copying problems. When you get to the page, use the browser print command to print as many as you wish. The printed output is not copyright.

Constructions pages on this site

Lines

Angles

Triangles

Right triangles

Triangle Centers

Circles, Arcs and Ellipses

Polygons

Non-Euclidean constructions