Trivia: Question about arranging terms

[salvomic]

(In this case increasing power order): Without any mathematical difference, what, if any, is the proper, or most formal way to express the ordering of the trig terms?
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In the old Italian books of trigonometry we have: SIN, COS, TAN and decreasing power order (x^4, x^3, x^2..., about my math professor), but if (generally) COS in x and SIN is y, we should have COS, SIN, TAN, I think...