If you cut the largest semicircle out of a rectangle with a length of 8 cm and a width of 4 cm, what is the area of the semicircle?
在一个长为8厘米，宽为4厘米的长方形中剪一个最大的半圆面，则这个半圆面的面积为多少π平方厘米
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<result>8</result>