A very common situation that I often run into when reading books and papers is that, the authors usually skip the underlying steps and jump straight to the final math expression, which has a rather different form compared with the original.
They say that the conclusion can be derived easily or obviously, but I am really unable to derive it. I can't even understand what each term in the result represents.
I tried searching on google, but nobody asked question concerning a specific step in a paper. I tried consulting my professor and the fellow classmates, but they admitted that they would never bother with a small question that doesn't affect the conclusion.
Where should I seek for help then? I don't even know which branch of math I need to look into. I was advised to ask question on math stackexchange, but it doesn't seem that there're enough people discussing here.