Two congruent circles intersect each other at points A and B. Through A any line segment PAQ is drawn so that P, Q lie on the two circles. Prove that BP = BQ.
AB is common chord in the given both triangles
So,
∠APB = ∠AQB
Now, in triangle BPQ
∠APB = ∠AQB
BQ = BP (Angles opposite to equal sides are equal)