The radius of the base of a cylinder is 2cm, and its sides are cut along the height to form a square. What is the height of the cylinder?
一个圆柱的底面半径是2cm，它的侧面沿高剪开是正方形，这个圆柱的高是多少．
<gadget id="calculator">2 * 3.14 * 2</gadget>
<output>12.56</output>

<result>12.56</result>