OKay so here are two examples: let say 1) f(x) = cos 2x + cos x how do you determine whether this function is periodic? I know I have to find period for each cosine. The first one is pi and second is 2pi. Then what do you do? And eventually, how do you determine the fundamental period? 2) this is what I got from class but the class ended so I rushed with the note. let say f(x) = cos 2x + 3sin (pi*x) according to my note, this is not a periodic. How so? and when I looked at the third examples, f(x) sin x - cos sqrt(2)*x, this is a periodic. I just couldn't find enough guide to help me (after looking up on google). Thank you for the help.