A is a point at a distance 13 cm from the centre O of a circle of radius 5 cm. AP and AQ are the tangents to the circle at P and Q. If a tangent BC is drawn at a point R lying on the minor PQ to intersect AP at B and AQ at C, find the perimeter of the ΔABC.
BP=BR and CR=CQ ( length of tangents drawn from an external point to a circle are equal )
Perimeter of triangle ABC = AB+BR+RC+CA
=AB+BP+QC+CA
=AP+QA ( AP=QA)
=2AP
In triangle APO, by Pythagoras theorem
AO2=AP2+PO2
132=AP2+52
AP2=144
⇒ AP = 12
Perimeter of triangle ABC = 2 x 12 = 24cm