The diameter of a circle is 8 cm, what is the area of the circle in square centimeters?
一个圆的直径是8厘米，这个圆的面积是多少平方厘米．
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</output>

<result>50.24</result>