There is a cylinder with a base radius of 2 decimeters, and its lateral expansion is exactly a square. What is the height of this cylinder?
有一个底面半径为2分米的圆柱体，它的侧面展开正好是一个正方形，这个圆柱体的高是多少．
<gadget id="calculator">3.14 * 2 * 2</gadget>
<output>12.56</output>

<result>12.56</result>