If the radius of the larger circle is 4 cm and the radius of the smaller circle is 2 cm, what is the area of the circle in square centimeters?
大圆的半径是4厘米，小圆的半径是2厘米，则圆环的面积是多少平方厘米．
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

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

<gadget id="calculator">16 - 4</gadget>
<output>12</output>

<gadget id="calculator">3.14 * 12</gadget>
<output>37.68</output>

<result>37.68</result>