Answer:
25
Step-by-step explanation:
AB is a tangent to the circle hence the angle ABO is a right angle !!! With that knowledge we can construct a right-angled triangle with sides AB ,BO and OA .
Applying the Pythagorean theorem we get that OA is the hypotenuse and thus
[tex]oa = \sqrt{ab {}^{2} + ob {}^{2} } [/tex]
