What is the area in square centimeters of a sector whose radius is 2 centimeters and whose central angle is (3/2) times the plane angle?
半径为2厘米，圆心角是平角的(3/2)倍的扇形面积为多少平方厘米．
<gadget id="calculator">180 / 360</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">(1/2) * 3.14 * 4</gadget>
<output>6.28</output>

<result>6.28</result>