What is the area of a sector with a radius of 2 cm and a central angle of 90°?
一个半径是2厘米，圆心角是90°的扇形的面积是多少平方厘米．
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

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

<result>3.14</result>