If the central angle of a sector is 72°, its area is equal to the area of a circle with the same radius. (fill in a fraction)
一个扇形的圆心角是72°，则它的面积相当于和它同半径的圆面积的多少．(填几分之几)
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>