If the central angle of a fan is doubled and the radius is doubled, how much will the resulting area be reduced?
一个扇形的圆心角增加2倍，半径缩小2倍，结果面积减少多少
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>