It is known that the diameter of the base of the cylinder is 6cm, and the side expansion is a square, find the height of the cylinder.
已知圆柱的底面直径是6cm，侧面展开是一个正方形，求圆柱的高．
<gadget id="calculator">3.14 * 6</gadget>
<output>18.84</output>

<result>18.84</result>