cylinder whose sides are expanded is a square, the radius of the base of the cylinder is 5 cm, what is the height of the cylinder in cm.
一个圆柱体的侧面展开是一个正方形，这个圆柱体的底面半径是5厘米，这个圆柱体的高是多少厘米．
<gadget id="calculator">2 * 3.14 * 5</gadget>
<output>31.4</output>

<result>31.4</result>