The perimeter of a square is 4dm, draw the largest circle in the square, what is the area of the circle?
正方形的周长是4dm，在正方形中画一个最大的圆，圆的面积是多少．
<gadget id="calculator">4 / 4 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) ** 2</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">3.14 * (1/4)</gadget>
<output>0.785</output>

<result>0.785</result>