If the base of a triangle is 2.5 cm and the height is 4.2 cm, what is its area in square centimeters?
一个三角形的底是2.5厘米，高是4.2厘米，它的面积是多少平方厘米．
<gadget id="calculator">4.2 / 2</gadget>
<output>2.1</output>

<gadget id="calculator">2.5 * 2.1</gadget>
<output>5.25</output>

<result>5.25</result>