I need help with this question:
f(x) = sin(2x) + cos(2x) where x is an element of [0,pie].
Find the interval on which this function is increasing and decreasing.
I know that I must calculate f'(x) > 0 and f'(x) < 0
But I'm not good at differentiating trigonometric functions and at finding the intervals.
I would very grateful for any help.