The side of a cylinder is expanded to form a square. The height of this cylinder is 25.12cm. What is the radius of its base?
一个圆柱的侧面展开后是一个正方形，这个圆柱的高是25.12cm，它的底面半径是多少．
<gadget id="calculator">25.12 / 3.14 / 2</gadget>
<output>4</output>

<result>4</result>