19. The area of a circle is 20.25 pi centimeters^2. Find the diameter. 20. If the radius of .C is 4 inches, find the area of the shaded sector. 21. The area of sector JLK is 4 pi in.^2 . Find m widehat JK. Solution pi r*R = 20.25pi r = 4.5 b) 3/4 pir*r = 12pi c) 4pi/64pi = theta/2pi 2pi/16 = pi/\'8 answer.