Mathematics in Ancient and Medieval India c6.s9.41

c6.s9.41

( c ) *The area of a cyclic quadrilateral* with sides a,b,c and d, is √((s-a)(s-b)(s-c)(s-d)) where 2s = a + b + c + d. This formula is given by Brahmagupta⁵ ( c. 628 A. D. ), Mahāvīra¹ ( c. 850 A. D. ), Śrīdhara² ( c. 850–950 A. D. ) and Bhāskara II,³ though these Indian scholars did not mention that the quadrilateral is cyclic. The proof may be obtained on the following lines.