Triangle is missing, so i have attached it.
Answer:
Radius = 10.82
Explanation:
From the image attached, the triangle is obviously a right angle triangle and therefore, the missing side (AB) which is the radius can be found via pythagoras theorem.
We are given;
AC = 21
BC = 18
Thus;
|AC|² = |AB|² + |BC|²
21² = |AB|² + 18²
|AB|² = 441 - 324
AB = √117
AB = 10.82