Bretschneider's Formula

Author

Eric W. Weisstein
March 6, 2004

This notebook downloaded from http://mathworld.wolfram.com/notebooks/PlaneGeometry/BretschneidersFormula.nb.

For more information, see Eric's MathWorld entry http://mathworld.wolfram.com/BretschneidersFormula.html.

©2005 Wolfram Research, Inc. except for portions noted otherwise

Formula

With[{s=(a+b+c+d)/2},
(s-a)(s-b)(s-c)(s-d)-(a c+b d+p q)(a c+b d-p q)/4]16//FullSimplify