Our mission is to find the area of ⊙ C, for which we will use the following formula.
A = π r^2
Before using the formula above, we need to find the radius of the circle. To do it, we recall that the diameter is twice the radius.
d = 2r ⇒ 20 &= 2r
⇒ r &= 10 in
Thus, to find the area we substitute r=20 into the formula above.
