If the sides of a cylinder are expanded along the height, it is a square with a side length of 31.4 cm. What is the area of its base in square centimeters?
一个圆柱的侧面沿高展开是边长为31.4厘米的正方形，它的底面积是多少平方厘米．
<gadget id="calculator">31.4 / 3.14 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<result>78.5</result>