A cylinder is a square when its sides are expanded. The diameter of the base of this cylinder is 4 cm. What is the height?
一个圆柱侧面展开是一个正方形，这个圆柱的底面直径是4厘米，高是多少？
<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>