An isosceles triangle top angle: base angle = 3:1, then how many degrees is a base angle.
一个等腰三角形顶角：底角=3：1，那么一个底角是多少度．
<gadget id="calculator">3 + 1 + 1</gadget>
<output>5</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">180 * (1/5)</gadget>
<output>36</output>

<result>36</result>