The central angle of a sector is 90°, what is the size of the sector
一个扇形的圆心角是90°，这个扇形的大小是所在圆的多少
<gadget id="calculator">90 / 360</gadget>
<output>1/4 = around 0.25</output>

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