It is known that the diameter of a circle is 8 cm. If a largest square is cut off from the circle, what is the area of the remaining part?
已知一个圆的直径是8厘米，在圆内剪去一个最大的正方形，剩余部分的面积是多少．
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</output>

<gadget id="calculator">8 * 4</gadget>
<output>32</output>

<gadget id="calculator">50.24 - 32</gadget>
<output>18.24</output>

<result>18.24</result>