What is the area of a semicircle with a radius of 0.2 meters?
半径是0.2米的半圆，它的面积是多少．
<gadget id="calculator">0.2 ** 2</gadget>
<output>0.04</output>

<gadget id="calculator">0.04 / 2</gadget>
<output>0.02</output>

<gadget id="calculator">3.14 * 0.02</gadget>
<output>0.0628</output>

<result>0.0628</result>