Answer:
7.0
Explanation:
Tangents form right angles, so AOB is a right triangle.
Now using Pythagorean Theorem (A^2 + B^2 = C^2), plug in the values and solve inversely.
5^2 + B^2 = 8.6^2
25 + B^2 = 73.96
B^2 = 48.96
B = squareroot 48.96
B = 6.997 --> 7.0