The diameter of the base of a cylinder is 2 cm, and the sides are exactly a square when the sides are unfolded. What is the side area of the cylinder in square centimeters?
一个圆柱的底面直径为2厘米，侧面展开后正好是一个正方形，这个圆柱的侧面积是多少平方厘米．
<gadget id="calculator">3.14 * 2</gadget>
<output>6.28</output>

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

<result>39.4384</result>