Question

are these functions periodic?

i - y=abs(sin(x)) = sin(x)
ii - y=cos(X^2)
iii - y = cos(sin(x))

I am completely lost on these :/

Answer 1

yes
no , http://www.wolframalpha.com/input/?i=cos%28x%5E2%29

yes , http://www.wolframalpha.com/input/?i=cos%28sin%28x%29%29