A circular wooden board, its diameter is 8cm, what is its area πcm**2.
一块圆形木板，它的直径是8cm，它的面积是多少πcm**2．
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<result>16</result>