Find a formula for the exact area, A, of the shaded region, which represents one-fourth of an annulus (ring). ( PLEASE JUST GIVE ME THE ANSWER)

Question

Find a formula for the exact area, A, of the shaded region, which represents one-fourth of an annulus (ring).

There are two concentric circles, two line segments, a marked angle, and two labeled lengths.

1. The first segment is horizontal, starts at the center of the circles and ends at a point on the left of the outer circle. Its entire length is labeled R.
2. The second segment is vertical, starts at the center of the circles and ends at a point on the top of the outer circle. The portion of the segment between the inner circle and the center of the circles is labeled with a length of r.
3. The angle above the first segment and to the left of the second segment is marked as a right angle.
4. The region that is above the first segment, to the left of the second line segment and between the two circles is shaded.

Answer 1

A = (0.25)(A_{big circle} - A_{small circle})