+128407 This one is a little difficult....
Assuming that CD is a tangent, ODC forms a right triangle with OC the hypotenuse and CD a leg
So....the other leg (OD) can be found with the Pythagorean Theorem.....note that OD = OB =the radius of the circle, r
OD = sqrt ( OC^2 - CD^2) and we can write
r = sqrt ( [CB + OB]^2 - CD^2 )
r = sqrt ( [ 14 + r ]^2 - 25^2 ) square both sides
r^2 = [14 + r ]^2 - 625
r^2 = 196 + 28r + r^2 - 625 subtract r^2 from both sides
0 = -429 + 28r add 429 to both sides
429 = 28r divide both sides by 28
15.3 = r
And the diameter is twice this = 30.6
