Write the interval for which the function `f(x) = cos x, 0 le x le 2pi` is decreasing

The function f(x)=cos x, 0 le x le pi is

Indicate the interval in which the function f(X) = cos x, 0lex le2pi , decreases.

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(x) = sin^4 x + cos^4x, 0 lex le pi/2 is strictly increasing or decreasing.

Write the interval in which the function f(x)=cos x is strictly decreasing.

Find the intervals in which the function f given by f(x)=sin x + cos x, 0 le x le 2 pi is Increasing or Decreasing.

Find the intervals in which the function f given by f(x)=sin x + cos x(0 le x le 2 pi) is decreasing