If the lateral expansion of a cylinder with a radius of 5 decimeters is a square, what is its lateral area?
半径为5分米的圆柱的侧面展开图是一个正方形，它的侧面积是多少平方分米．
<gadget id="calculator">2 * 3.14 * 5</gadget>
<output>31.4</output>

<gadget id="calculator">31.4 * 31.4</gadget>
<output>985.96</output>

<result>985.96</result>