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Bretschneider's formula

Revision as of 17:41, 21 June 2006 by Inscrutableroot (talk | contribs) (proofreading)

Let us have a quadrilateral with side lengths $a,b,c,d$, and diagonals $p, q$. Bretschneider's formula says that $[ABCD]=\frac{1}{4}*\sqrt{4p^2q^2-(b^2+d^2-a^2-c^2)^2}$. It is derived through vector geometry.

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