If the lengths of the three sides of a right triangle are 3 cm, 4 cm, and 5 cm, what is its area?
一个直角三角形三条边的长度分别是3厘米、4厘米、5厘米，它的面积是多少．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<result>6</result>