A cylinder is a square if its sides are expanded. The radius of the base of the cylinder is 2 cm. What is the height of the cylinder in cm?
一个圆柱的侧面展开是正方形，圆柱的底面半径是2厘米，圆柱的高是多少厘米．
<gadget id="calculator">3.14 * 2 * 2</gadget>
<output>12.56</output>

<result>12.56</result>