If a cylinder with a base radius of 4 cm is square when its sides are expanded, what is the height of the cylinder in cm?
一个底面半径是4厘米的圆柱侧面展开后是正方形，则圆柱高多少厘米．
<gadget id="calculator">2 * 3.14 * 4</gadget>
<output>25.12</output>

<result>25.12</result>