What is the area of a semicircle whose circumference is 25.7 cm?
一个周长是25.7cm的半圆，面积是多少．
<gadget id="calculator">25.7 / 5.14</gadget>
<output>5</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">3.14 * 5 * (5/2)</gadget>
<output>39.25</output>

<result>39.25</result>