Problem: Tangents AB and AC are drawn to a circle from exterior point A. Tangent PQR intersects AB in P and AC in R, and touches the circle at Q. If AB=20, then the perimeter of triangle APR is:
Answer Choices:
A. 42
B. 40.5
C. 40
D. 3987​
E. not determined by the given information.
Solution:
p (perimeter of triangle APR ) =AP+PQ+RQ +RA , and PQ=PB and RQ=RC
∴p=AP+PB+RC+RA=AB+AC=20+20 =40.