The side view of a cylinder is a square. If the height increases by 2 centimeters, the surface area increases by 12.56 square centimeters. What is the original side area of the cylinder in square centimeters?
一个圆柱体的侧面展开图是正方形，如果高增加2厘米，表面积就增加12.56平方厘米，则原来这个圆柱的侧面积是多少平方厘米．
<gadget id="calculator">12.56 / 2</gadget>
<output>6.28</output>

<gadget id="calculator">6.28 * 6.28</gadget>
<output>39.4384</output>

<result>39.4384</result>