The side of a cylinder is expanded along the height to form a rectangle with a length of 12.56cm and a width of 6.28cm. Find the radius of the bottom surface of the cylinder.
一个圆柱的侧面沿高展开式一个长12.56cm，宽6.28cm的长方形，求这个圆柱的底面半径．
<gadget id="calculator">12.56 / 2 / 3.14</gadget>
<output>2</output>

<result>2</result>