Expand the sides of a cylinder to obtain a square. The radius of the base of the cylinder is 5 cm. What is the height of the cylinder?
把一个圆柱体的侧面展开，得到一个正方形，这个圆柱体的底面半径是5厘米，圆柱体的高是多少．
<gadget id="calculator">2 * 3.14 * 5</gadget>
<output>31.4</output>

<result>31.4</result>