Cut a semicircle on a piece of paper with a length of 3 cm and a width of 1 cm. What is the area of the semicircle?
在一个长3cm，宽1cm的纸上剪上一个半圆，这个半圆的面积是多少．
<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 * 3.14 * (1/2)</gadget>
<output>1.57</output>

<result>1.57</result>