A cylinder with a base radius of 5 cm is exactly a square. What is the height of this cylinder in cm?
一个底面半径5cm的圆柱的侧面展开正好是一个正方形．这个圆柱高多少cm．
<gadget id="calculator">2 * 3.14 * 5</gadget>
<output>31.4</output>

<result>31.4</result>