The ratio of the base angle of an isosceles triangle to its top angle is 2:5, what is its top angle?
等腰三角形一个底角度数与它的顶角的比是2：5，它的顶角度数是多少度．
<gadget id="calculator">2 + 2 + 5</gadget>
<output>9</output>

<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">180 * (5/9)</gadget>
<output>100</output>

<result>100</result>