# Copy an Angle

## Copy an Angle

We start with angle A, and point B on one side of angle A. Construct a circle with center at A that has a radius about half the length of segment AB. Mark the intersections of the sides of angle A and the circle. The top is point C and the bottom is D. Copy the circle with radius AC and center A to a circle with center at B. This new circle intersects ray AB at two points. Mark the intersection of the top point, point E. We will measure how far along the arc of the circle it is from C to D using the compass tool. With the compass tool, mark radius CD and then copy that circle to a center at point E. (We want to know how far of an arc along the circle that goes through point E that would be the same distance as it is from C to D.) Mark the lower intersection of your two circles as point F. Construct line BF. Move point B and watch what happens. You can also change the size of the circle at A by moving point C if that would help you see it better. What can you say about ray AC and line BF? Why?