In an isosceles triangle, the ratio of the top angle to the bottom angle is 4:1, then, what is the top angle of this isosceles triangle?
一个等腰三角形，它的顶角和一个底角的比是4：1，那么，这个等腰三角形顶角是多少度．
<gadget id="calculator">4 + 1 + 1</gadget>
<output>6</output>

<gadget id="calculator">4 / 6</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">180 * (2/3)</gadget>
<output>120</output>

<result>120</result>