Brahmagupta's Formula
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http://jwilson.coe.uga.edu/emt725/brahmagupta/brahmagupta.html  


Jim Wilson, Dept. of Mathematics Education, Univ. of Georgia  
Problem: Develop a proof for Brahmagupta's Formula, which provides the area A of a cyclic quadrilateral (i.e., a simple quadrilateral inscribed in a circle) with sides of length a, b, c, and d as A = sqrt((sa)(sb)(sc)(sd)) where s is the semiperimeter (a+b+c+d)/2. There are alternative approaches to this proof. The one outlined here is intuitive and elementary; a more elegant approach is available using trigonometry. From a course on Problem Solving in Mathematics.  


Levels:  College 
Languages:  English 
Resource Types:  Course Notes 
Math Topics:  Conic Sections and Circles, Triangles and Other Polygons, Trigonometry 
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