Given that the perimeter of an isosceles triangle is 16 cm, the waist length is 5 cm, and the height above the base is 4 cm, find the area of the triangle.
已知等腰三角形的周长是16厘米，腰长5厘米，底边上的高是4厘米，求三角形的面积．
<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>