A CIRCLE IS TANGENT TO A LINE AT A. FROM A POINT P ON...
4. A circle is tangent to a line at A. From a point P on the circle, a line is drawn
such that PN is perpendicular to AN. If PN = 9 and AN = 15, determine the radius
of the circle.
P
A N
【Solution】
Let O be the center of the circle. Complete the
rectangle ANPQ. Let r be the radius of the circle.
Then
O
=
2
2
r OP
Q
= +
OQ QP
= − +
OA PN AN
( )
2