# Thread: increasing and decreasing functions

1. ## increasing and decreasing functions

For the function f(x)=sin(x)+cos(x) on the interval (0, 2pi) I am supposed to find where f(x) is increasing or decreasing. I took the derivative of the function and came up with f'(x) = cos(x)-sin(x) which i set equal to zero, what do I need to do next?

2. Originally Posted by sydewayzlocc
For the function f(x)=sin(x)+cos(x) on the interval (0, 2pi) I am supposed to find where f(x) is increasing or decreasing. I took the derivative of the function, what do I need to do next?
It's increasing when $f'(x) > 0$ and decreasing when $f'(x) < 0$.

3. Originally Posted by Prove It
It's increasing when $f'(x) > 0$ and decreasing when $f'(x) < 0$.
Don't I need to find the critical numbers and make a table

4. Do that and then use what Prove It said.