The way to express "cosine squared" in words, without including "cosine" or "squared", would be a lesson in cosines and a lesson in squaring. So you're correct, but why is this point useful?
English/natural language isn't a privileged mode. It's one of many, including math, musical notation, computer code, and chess notation. We use the best language for the context, and who cares that laborious translations are available to others? I could be typing ascii codes in binary, instead of letters right now, but so what?