Brahmagupta's formulaBrahmaguptasFormula2001-10-06 18:20:342001-10-31 00:12:51TheoremAreaQuadrilateralCyclic\usepackage{amssymb}
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If a cyclic quadrilateral has sides $p,q,r,s$ then its area is given by
$$\sqrt{(T-p)(T-q)(T-r)(T-s)}$$
where $T=\frac{p+q+r+s}{2}$.
Note that if $s\to 0$, Heron's formula is recovered.
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