The area of a sector is (1/5) the area of a circle with the same radius, and the length of the arc contained in this sector is the length of the circumference of a circle with the same radius
一个扇形的面积是同半径圆面积的(1/5)，这个扇形所含圆弧的长是同半径圆周长的多少
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>