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Bretschneider's formula

Revision as of 22:06, 30 June 2006 by JBL (talk | contribs)

Suppose we have a quadrilateral with sides of length $a,b,c,d$ and diagonals of length $p, q$. Bretschneider's formula states that $[ABCD]=\frac{1}{4}*\sqrt{4p^2q^2-(b^2+d^2-a^2-c^2)^2}$.

It can be derived with vector geometry.

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