It is known that the degree ratio of the two acute angles of a right triangle is 1:4, what is the smallest angle in this triangle?
已知一个直角三角形的两个锐角的度数比是1﹕4，这个三角形中最小的那个角是多少度？
<gadget id="calculator">1 + 4</gadget>
<output>5</output>

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

<gadget id="calculator">90 * (1/5)</gadget>
<output>18</output>

<result>18</result>