To construct a pentagon, draw a line AB. Just like the Equilateral Triangle, construct circles [arcs] around A and B with radius AB. Where the arcs intersect, put a point R. Next construct the perpendicular bisector of line segment AB. Still using the same radius, and center R, draw an arc through point A, intersecting the left circle and the perpendicular bisector as shown. Draw a line between those two points. Where the line intersects the circle whose center is B, put a point. Draw a line segment from that point to B. Repeat this process on the other side (flipped but not shown) and connect all of the vertices to make a pentagon.

This method was used by masons in the middle ages to construct regular pentagons. It is not exact. However, it is a good aproximation of one.

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