What is the area of a semicircle surrounded by 10.28 cm iron wire?
用10.28厘米的铁丝围成一个半圆形，它的面积是多少平方厘米．
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

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

<gadget id="calculator">3.14 * 2</gadget>
<output>6.28</output>

<result>6.28</result>