Divide a circle into several equal parts, cut it and put it together into an approximate rectangle. The area of the shadow is known to be 9.42 square centimeter. What is the area of the circle

Divide a circle into several equal parts, cut it and put it together into an approximate rectangle. The area of the shadow is known to be 9.42 square centimeter. What is the area of the circle

9.42 x 2 = 18.84 (cm2)

It is known that the area of the circle in the right figure is equal to the area of the rectangle, and the length of the rectangle is 9.42 cm. Calculate the area and perimeter of the shadow part

π*r^2=OB*BC r=OB
If π * R ^ 2 = R * 9.42, r = 3
Shadow area s = 3 * 9.42-0.25 * (π * 3 ^ 2) = 21.192
Perimeter L = 9.42 + 3 + (9.42-3) + 0.25 * (π * 6) = 23.55

As shown in the figure, the area of the circle is 31.4 square centimeters. What is the area of the shadow?

31.4 △ 3.14 = 10 (square centimeter) 4 × 10 = 40 (square centimeter) a: the area of shadow is 40 square centimeter