It is known that the ratio of the apex angle to the base angle of an isosceles triangle is 1:4, what is the smallest angle in this triangle?
已知一个等腰三角形的顶角和底角度数比是1﹕4，这个三角形中最小的那个角是多少度？
<gadget id="calculator">1 + 4 + 4</gadget>
<output>9</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">180 * (1/9)</gadget>
<output>20</output>

<result>20</result>