The area of a square is 16 square centimeters. If a largest semicircle is drawn in this rectangle, what is the area of this semicircle in square centimeters?
正方形的面积是16平方厘米，如果在这个长方形中画一个最大半圆，这个半圆的面积是多少平方厘米．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

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

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

<result>6.28</result>