To construct a regular pentagon in a circle with radius AB. Let the circle with center A and radius AB be drawn. Erect a perpendicular line to the radius AB at the center A so that it intersects the circle at point C. Let D be the midpoint of the line AC. Connect the points D and B with a straight line. Bisect the angle ADB with line DE so that the point E lies on the radius AB. Erect a perpendicular line to the radius AB at the point E so that it intersects the circle at the point F. Then the line BF will be one side of a pentagon.

David E. Joyce
Department of Mathematics and Computer Science
Clark University
Worcester, MA 01610

Email: djoyce@clarku.edu
My nonJava Homepage and my Java homepage