The radius of a circle is 2 cm, what is the area of the circle in cm
一个圆的半径是2cm，这个圆的面积是多少cm
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>