6. ABCD is such a quadrilateral that A is the centre of the circle passing through B, C and D. Prove that ∠CBD + ∠CDB = 1/2 ∠BAD 6. ABCD is such a quadrilateral that A is the centre of the circle passing through B C and D. Prove that ∠CBD + ∠CDB = 1/2 [...]