Pentagon

in geometry, a plane figure consisting of five angles, and consequently five sides also. If the angles be all equal, it is a regular pentagon. t is a remarkable property of the pentagon, that its side is equal in power to the sides of a hexagon and a decagon inscribed in the same circle; that is, the square of the side of the pentagon, is equal to both the squares taken together of the sides of the other two figures; and consequently those three sides will constitute a right-angled triangle. To find the area of a regular pentagon, multiply the square of its side into the number 1.7204774,