The lateral expansion of a cylinder is a square. It is known that the radius of the base of the cylinder is 4 cm. What is the height of the cylinder in cm?
一个圆柱的侧面展开是正方形，已知圆柱底面半径是4厘米，圆柱的高是多少厘米．
<gadget id="calculator">3.14 * 2 * 4</gadget>
<output>25.12</output>

<result>25.12</result>