A semicircle is formed by a 10.28m rope, what is the area of the semicircle in square meters?
用一根10.28米的绳子围成一个半圆形，这个半圆的面积是多少平方米．
<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>