The base of a triangle is 7.8cm, what is the area in cm**2, and its height is 4cm.
一个三角形的底是7.8cm面积是多少cm**2，它的高才是4cm．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">7.8 * 2</gadget>
<output>15.6</output>

<result>15.6</result>