No. This thread is not at all about foundations of math; it's about, a.o., entropy of multisets, as witnessed in the OP. Your "off topic" reaction is a case of the pot blaming the kettle.
Moreover, by your own reasoning - that this thread is about foundations of math - TMiguel's post is most appropriate. His post is namely not about Trig, but about proof theory, and his case of a Trig theorem is just a particular instance of that.
Your corpus of posts shows such a profound lack of understanding of mathematics, that, IMHO, TMiguel's little test to see if you can write up a proof of such a simple theorem is more than warranted. In fact, I'll give you a little test below.
A nonsensical remark in this context, and then I'm being nice.
My test:
Prove the Theorem of Pythagoras.
Hint: draw a square with side a+b, where a and b are the lengths of the legs of the right triangle.