In figure PA and PB are tangents from P to the circle with centre O. R is a point on the circle. Prove that : PC + CR = PD + DR
We have
PB = PA = 12 cm
and CQ = CA = 3 cm
[∴ Tangent from external point to a circle are equal in length]
Now,
Length of PC = PA – CA
= 12 – 3
= 9 cm.