The perimeter of an isosceles triangle is 16dm, the waist length is 5dm, and the height above the base is 4dm. What is its area in d㎡?
等腰三角形的周长是16dm，腰长5dm，底边上的高是4dm，它的面积是多少d㎡．
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">16 - 10</gadget>
<output>6</output>

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

<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<result>12</result>