Question

AB is tangent to circle O at B. what is the length of the radius r? Round to the nearest tenth. Look at image attached.

Answer 1

Check the picture below.

Answer 2

OAB is a right triangle. Of this triangle, you know the hypothenuse (OA) and the longest leg (AB). You can find the radius, which is the shortest leg, by applying Pitagora.

r (OB) = √OA²-AB² = √9,8²-5² = √96,04-25 = √71,04 ≈ 8,4 (units?)

Answer D