Answer:
see explanation
Step-by-step explanation:
If AB is a tangent then ∠ ABC = 90° and Δ ABC is right
Using the converse of Pythagoras' identity
If the square of the longest side is equal to the sum of the squares on the other 2 sides.
15 is the longest side and 15² = 225
9² + 12² = 81 + 144 = 225
Thus Δ ABC is a right triangle at B
Thus AB is a tangent to the circle at B
