#### Question

ABCD is a cyclic quadrilateral in which AB and DC on being produced, meet at P such that PA

= PD. Prove that AD is parallel to BC.

#### Solution

Let ABCD be the given cyclic quadrilateral

Also, PA = PD (Given)

∴ ∠PAD = ∠PDA ……..(1)

∴ ∠BAD = 180° - ∠PAD

And ∠CDA = 180° - PDA = 180° - ∠PAD (From (1))

We know that the opposite angles of a cyclic quadrilateral are supplementary

∴ ∠ABC = 180° - ∠CDA = 180° - (180° - ∠PAD) = ∠PAD

And ∠DCB = 180° - ∠BAD = 180° - (180° - ∠PAD) = ∠PAD

∴ ∠ABC = ∠DCB = ∠PAD = ∠PAD

That means AD || BC

Is there an error in this question or solution?

Solution Abcd is a Cyclic Quadrilateral in Which Ab and Dc on Being Produced, Meet at P Such that Pa = Pd. Prove that Ad is Parallel to Bc. Concept: Cyclic Properties.