The upper base of a trapezoid is 3cm, the lower base is 5cm, and the height is 4cm. Draw a largest triangle inside. What is the area of this triangle in cm**2.
一个梯形的上底是3cm，下底是5cm，高是4cm，在里面画一个最大三角形，这三角形的面积是多少cm**2．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<result>10</result>