The lateral expansion of a cylinder is a square. If the height increases by 2 cm, the surface area increases by 12.56 cm2. What is the lateral area of the cylinder in square centimeters?
一个圆柱的侧面展开是一个正方形．如果高增加2厘米，表面积增加12.56平方厘米．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>