Rhombus
A parallelogram with four congruent sides. Note that the diagonals of a rhombus are perpendicular (as is the case with all kites).
Note: A square is a special kind of rhombus.
s = side length of rhombus h = height of rhombus d1 = long diagonal of rhombus d2 = short diagonal of rhombus
Area = hs = s2 sin A = s2 sin B = (½) d1d2
See also
Quadrilateral, trapezoid, area of a rhombus, sine