If the diameter of a circle is 6 decimeters, what is the area of π square decimeters?
一个圆的直径是6分米，面积为多少π平方分米．
<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<result>9</result>