The three sides of a right triangle are 3 cm, 4 cm and 5 cm respectively, what is the area in cm**2.
直角三角形三边分别是3厘米、4厘米和5厘米，面积是多少厘米**2．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

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

<result>6</result>