The three sides of a right triangle are 5cm, 9cm and 12cm respectively, what is its area in cm**2.
一个直角三角形的三条边分别是5cm，9cm和12cm，它的面积是多少cm**2．
<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">5 * (9/2)</gadget>
<output>45/2 = around 22.5</output>

<result>45/2 = around 22.5</result>