After unfolding the sides of a cylinder with a base diameter of 4 cm, a square is obtained. What is the height of the cylinder in centimeters?
把一个底面直径是4厘米圆柱体的侧面展开后，正好得到一个正方形，圆柱体的高是多少厘米．
<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>