If the circumference of a circle is 6.28 cm and the radius increases by 1 cm, how many square centimeters does the area increase?
一个圆的周长是6.28厘米，半径增加1厘米，面积增加了多少平方厘米？
<gadget id="calculator">6.28 / 3.14 / 2</gadget>
<output>1</output>

<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

<gadget id="calculator">1 + 1</gadget>
<output>2</output>

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

<gadget id="calculator">3.14 * 1 * 4</gadget>
<output>12.56</output>

<gadget id="calculator">3.14 * 1</gadget>
<output>3.14</output>

<gadget id="calculator">12.56 - 3.14</gadget>
<output>9.42</output>

<result>9.42</result>