The ratio of the top angle to the bottom angle of an isosceles triangle is 2:5, what is its top angle?
等腰三角形的顶角与一个底角的比是2：5，它的顶角是多少．
<gadget id="calculator">2 + 5 + 5</gadget>
<output>12</output>

<gadget id="calculator">2 / 12</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">180 * (1/6)</gadget>
<output>30</output>

<result>30</result>