Find the intervals in which the function given by `f(x)=sin x+cos x, 0le x le 2pi` is strictly increasing.

Find the intervals in which the function 'f' given by: f(x) = sin x-cosx , 0 le x le 2pi is strictly increasing or decreasing.

Find the intervals in which the function given by : f (x) = sin x + cos x , 0 le x le 2pi . is strictly increasing and strictly decreasing.

Find the intervals in which the function: f(x) = sin^4 x + cos^4x, 0 lex le pi/2 is strictly increasing or decreasing.

Find the intervals in which the function f given by f(x) = sinx + cosx, 0lexle2pi is increasing

Find the intervals in which the function f given by f(x) = x^2 - 4x + 6 , is strictly decreasing.