Given: PQ and RS are the two common tangent to the two circle
To Proof: A is the point of intersection of PQ and RS
We know that , length of two tangent drawn from an exterior point to acirclr are equal.
Therefore
PA = RA----------------- (i)
QA = SA ------------------- (ii)
Adding two equations we get
PA + QA = RA + SA
PQ =RS (proved)