In the given figure, a circle touches the side BC of △ABC at P and AB and AC produced at Q and R respectively. If AQ=15 cm, then the perimeter of △ABC is
We know that
AQ=AR [Tangents from an external point on the circle are equal in length]
⇒AQ=AC+CR
But, CR=CP [Tangents from an external point on the circle are equal in length]
Therefore, AQ=AC+CP …..(i)
Also, AQ=AB+BQ
But, BQ=BP [Tangents from an external point on the circle are equal in length]
∴AQ=AB+BP .….(ii)
Adding equations (i) and (ii)
2AQ=AC+CP+BP+AB
⇒2AQ= Perimeter of △ABC
⇒ Perimeter of △ABC =2×15=30 cm