Congruent segments are segments which have equal lengths. How can you use a compass and straight edge to construct a segment that is congruent to a given segment?

Click on the image below to view an animation on copying a line segment. View the animation by clickin the RUN button, or step through the procedures, one at a time, using the NEXT button. Close the window when you finish to get back to the lesson.

Please respond to the following questions in your notes.

1. Why does the construction for congruent segments work? (Hint: If you had drawn a complete circle with your compass instead of an arc, how would the length of the original segment compare to the radius of the new circle?)
2. How could you perform a similar construction using patty paper?

To summarize, if you are asked to construct a segment congruent to a given segment, or copy the given segment, you may have a construction that looks like this:

In this construction, AB is copied onto the second line by marking out the distance between points A and B, then marking that same distance from point C and labeling it point K.