The lateral expansion of a cone is a sector with a radius of 12 cm and a central angle of 90 degrees. What is the area of its base in square centimeters?
圆锥的侧面展开是一个半径是12厘米，圆心角是90度的扇形，它的底面积是多少平方厘米．
<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9</gadget>
<output>28.26</output>

<result>28.26</result>