The perimeter of an isosceles triangle is 16 decimeters, the length of the waist is 5 decimeters, and the height of the base is 4 decimeters. What is its area in square decimeters?
一个等腰三角形的周长是16分米，腰长5分米，底边上的高是4分米，它的面积是多少平方分米．
<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>