Rhombus

A rhombus is a quadrilateral with both pairs of opposite sides parallel and all sides the same length, i.e., an equilateral parallelogram. The word rhomb is sometimes used instead of rhombus, and a rhombus is sometimes also called a diamond. A rhombus with is sometimes called a lozenge.

The polygon diagonals and of a rhombus are perpendicular and satisfy

(1)

The diagonals are related to the opening angle by

			(2)
			(3)

The area of a rhombus is given by

			(4)
			(5)
			(6)

The rhombus is a tangential quadrilateral with , and so has inradius

			(7)
			(8)