History of Hindu Mathematics: A Source Book v2.c17.s19.t1.48

v2.c17.s19.t1.48

Bhâskara II points out that the diagonals of the Brahmagupta quadrilateral are in the (A) variety, $2pq(m² - n²) + 2mn(p² - q²), 4mnpq + (p² - q²)(m² - n²) ;$ in (B), $2pq(m² - n²) + 2mn(p² - q²), (p² + q²)(m² + n²) ;$ and in (C), $4mnpq + (p² - q²)(m² - n²), (p² + q²)(m² + n²).$ The diameter of the circumscribed circle in every case is (p² + q²)(m² + n²).