Find the lateral area of a cylinder: the radius of the base is 8 cm, and the height is 5 cm.
求圆柱的侧面积：底面半径是8cm，高是5cm．
<gadget id="calculator">2 * 3.14 * 8 * 5</gadget>
<output>251.2</output>

<result>251.2</result>