A step-by-step ruler and compass construction of a regular pentagon. The construction is due to H. W. Richmond, “A Construction for a Regular Polygon of Seventeen Sides,” Quart. J. Pure Appl. Math., 26, 1893 pp. 206–207.
A regular pentagon is a five-sided polygon with sides of equal length and interior angles of 108° (3?/5 rad). Because 5 is a Fermat prime, you can construct a regular pentagon using only a straightedge and compass.
