Draw the largest circle in a square with a circumference of 28 cm. What is the area of the circle?
在一个周长是28厘米的正方形里画一个最大的圆，圆的面积是多少．
<gadget id="calculator">28 / 4 / 2</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">(7/2) ** 2</gadget>
<output>49/4 = around 12.25</output>

<gadget id="calculator">3.14 * (49/4)</gadget>
<output>38.465</output>

<result>38.465</result>