Rhombus
From Conservapedia
A rhombus is an equilateral quadrilateral, which is a polygon having four sides of equal length.
A square is a special case of a rhombus where all four interior angles are ninety degrees.
In non-academic contexts, the term diamond can be applied to a rhombus, particularly if it is oriented with one of its diagonals vertical.[1]
Its area is the product of its diagonals divided by two. Note that its diagonals are perpendicular to each other, and bisect each other.
In symbolic form, the area of a rhombus having diagonals of lengths D1 and D2 is:
This area also equals the length of a side (B) multiplied by the length of the perpendicular between two opposite sides (H):
