A wire can just enclose a circle with a diameter of 8 cm. If it encloses a square, what is the side length of the square in cm?
一根铁丝刚好能围成一个直径是8cm的圆，若把它围成一个正方形，正方形的边长是多少cm．
<gadget id="calculator">8 / 4</gadget>
<output>2</output>

<gadget id="calculator">3.14 * 2</gadget>
<output>6.28</output>

<result>6.28</result>