Use a semicircular piece of paper with a diameter of 16 cm to make the side of a cone. What is the area of the base of the cone in square centimeters?
用直径16厘米的半圆形纸片，做一个圆锥的侧面，这个圆锥的底面积是多少平方厘米．
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</output>

<result>50.24</result>