The radius of the base of a cylinder is 5 cm, and the sides are unfolded to form a square. What is the height of the cylinder in cm?
一个圆柱的底面半径是5厘米，侧面展开后正好是一个正方形，圆柱的高是多少厘米．
<gadget id="calculator">3.14 * 2 * 5</gadget>
<output>31.4</output>

<result>31.4</result>