The upper base of a right-angled trapezoid is 3 cm, the lower base is 6 cm, and the height is 3 cm. Cut out the largest circle in this trapezoid. Find the area of the remainder.
直角梯形上底3厘米，下底6厘米，高3厘米，在这个梯形内剪下一个最大圆．求剩余部分的面积．
<gadget id="calculator">3 + 6</gadget>
<output>9</output>

<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">9 * (3/2)</gadget>
<output>27/2 = around 13.5</output>

<gadget id="calculator">(3/2) ** 2</gadget>
<output>9/4 = around 2.25</output>

<gadget id="calculator">3.14 * (9/4)</gadget>
<output>7.065</output>

<gadget id="calculator">(27/2) - 7.065</gadget>
<output>6.435</output>

<result>6.435</result>