If any quadrilateral ABCD has
sides of lengths a, b, c, and d, and the semi-perimeter
, then
the area is given by:


Brahmagupta (598–668) was an Indian
mathematician and astronomer who discovered a neat formula for
the area of a cyclic quadrilateral.
See also:
Brahmagupta's Theorem,
Corollary,
Area Formula,
Area Formula Extension.

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