Circle O is tangent to AB at A, and angle ABD = 90 degrees. If AB = 12 and CD = 16, find the radius of the circle.
Bisect CD at M
MD = 8
Draw OM = BA = 12
We have right triangle DOM where OD = the radius of the circle and hypotenuse of DOM
Using the Pythagorean Theorem
OD =sqrt ( OM^2 + MD^2 ) = sqrt ( 12^2 + 8^2) = sqrt ( 144 + 64) = sqrt (208) = 4sqrt (13) = the radius