In the given figure, an isosceles triangle ABC, with AB = AC, circumscribes a circle. Prove that the point of contact P bisects the base BC.
The tangents drawn from an externel point to a circle are equal in length.
∴ AP = AQ ............ (1)
BP = BR ................ (2)
CQ = CR .............. (3)
Given that ABC is an isosceles triangle with AB = AC.
Subtract AP on both sides, we obtain
AB – AP = AC – AP
⇒ AB – AP = AC – AQ (from (1))
∴ BP = CQ.
⇒ BR = CQ (from (2))
⇒ BR = CR (from (3))
∴BR = CR, it shows that BC is bisected at the point of contact R