Indian Mathematics c12.s2.100

c12.s2.100

If A² + B² = C², and a² + b² = c² then the quadrilateral Ac, Bc, aC, bC is cyclic and the diagonals are Ab + aB and Aa + Bb, the area is ½ (ABc² + abC²), &c. In the present case A = 15, B = 20, C = 25; a = 5, b = 12, c = 13. The diagonals are 315, 280; the area 44100. For full details see the *Līlāvatī*, § 193.