Answer:
AC ≈ 12
Explanation:
the angle between the tangent AC and the radius BC is 90°
then Δ ABC is right
note that BC = 9 ( radius of circle )
using Pythagoras' identity in the right triangle
AC² + BC² = AB²
AC² + 9² = (9 + 6)² = 15²
AC² + 81 = 225 ( subtract 81 from both sides )
AC² = 144 ( take square root of both sides )
AC =
= 12