If the radius of the circle r=40cm, then the central angle is 72. What is the area of the sector of .
如果圆的半径r=40cm，那么圆心角为72．的扇形的面积是多少．
<gadget id="calculator">40 ** 2</gadget>
<output>1_600</output>

<gadget id="calculator">72 * 3.14 * 1_600</gadget>
<output>361_728</output>

<gadget id="calculator">361_728 / 360</gadget>
<output>5_024/5 = around 1_004.8</output>

<result>5_024/5 = around 1_004.8</result>