Answer:
radius = 5
Explanation:
Since the line is a tangent, that means the PT and OP are perpendicular (they make a right angle) Sooo, the triangle is a right triangle. Use Pythagorean Theorem to calculate or Pythagorean Triples for a shortcut (5, 12, 13)
r^2 + 12^2 = 13^2
r^2 + 144 = 169
Subtract 144
r^2 = 25
Squareroot both sides.
sqrt(r^2) = sqrt25
r = 5
The radius is 5.