The area of a sector with a central angle of 72° is equal to the area of the circle on which it is located.
圆心角为72°的扇形面积是所在圆面积的多少．
<gadget id="calculator">72 / 360</gadget>
<output>1/5 = around 0.2</output>

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