A wire encloses a square with a side length of 1.57 decimeters. If it encloses a circle, what is the radius of the circle in decimeters?
一根铁丝围成一个正方形，边长是1.57分米，如果围成一个圆，这个圆的半径是多少分米．
<gadget id="calculator">4 / 3.14 / 2</gadget>
<output>0.636943</output>

<gadget id="calculator">1.57 * 0.636943</gadget>
<output>1.000001</output>

<result>1.000001</result>