The radius of the top of a round coffee table is 0.5 meters, what is its area in square meters?
一个圆形茶几桌面的半径是0.5米，它的面积是多少平方米？
<gadget id="calculator">0.5 ** 2</gadget>
<output>0.25</output>

<gadget id="calculator">3.14 * 0.25</gadget>
<output>0.785</output>

<result>0.785</result>