The area of a sector is equal to (1/4) of the area of the circle it is in, what is the central angle of the sector.
一个扇形的面积等于它所在圆的面积的(1/4)，这个扇形的圆心角是多少．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">360 * (1/4)</gadget>
<output>90</output>

<result>90</result>