If the radius of a semicircle is 3 cm, what is its circumference in cm?
一个半圆的半径是3厘米，它的周长是多少厘米．
<gadget id="calculator">3.14 * 3</gadget>
<output>9.42</output>

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">9.42 + 6</gadget>
<output>15.42</output>

<result>15.42</result>