If a cylinder with a base radius of 2.5 cm is expanded to form a square, what is the height of the cylinder in cm?
把一个底面半径是2.5cm的圆柱体侧面展开后得到一个正方形，这个圆柱的高是多少cm．
<gadget id="calculator">2 * 3.14 * 2.5</gadget>
<output>15.7</output>

<result>15.7</result>