circle geometry

Area of circle    -    area of rectangle = shaded area

circle area = pi r^2      need to find   'r'    

          the diagonal of the rectangle is the DIAMETER

              via pythagorean theorem    diagonal =   sqrt ( 6^2 + 8^2) = 10

                        so radius = 5

pi *  5²       -          6 * 8    =   shaded area