The circumference of the outer circle of a ring is 62.8cm, and the circumference of the inner circle is 56.52cm. What is the area of half the circle?
一个圆环外圆的周长62.8cm，内圆周长是56.52cm，半个圆环面积多少．
<gadget id="calculator">62.8 / 3.14 / 2</gadget>
<output>10</output>

<gadget id="calculator">3.14 * 10 * 10</gadget>
<output>314</output>

<gadget id="calculator">56.52 / 3.14 / 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9 * 9</gadget>
<output>254.34</output>

<gadget id="calculator">314 - 254.34</gadget>
<output>59.66</output>

<gadget id="calculator">59.66 / 2</gadget>
<output>29.83</output>

<result>29.83</result>