The radius of the sector is 9 cm, and the central angle is 20 degrees. What is the area of the sector in square centimeters?
扇形的半径是9厘米，圆心角是20度，这个扇形的面积是多少平方厘米．
<gadget id="calculator">9 ** 2</gadget>
<output>81</output>

<gadget id="calculator">20 / 360</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">3.14 * 81 * (1/18)</gadget>
<output>14.13</output>

<result>14.13</result>