For two sectors in the same circle, the central angle of the large sector is twice that of the small sector, and the area of the small sector is what the area of the large sector is
同圆中的两个扇形，大扇形的圆心角是小扇形的2倍，小扇形的面积是大扇形的多少
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>