i'd like your thoughts on this one. thank you!

Find the intervals on which f is increasing/decreasing and state any relative extremaSo I find the derivative to find the critical numbers:1)

So I set that equal to zero:

Divide by -2:

Add :

Sub :

Divide by :

So:

So I went on the unit circle and found all the places where the x coordinate is one half and included the negative of those angles angles since

Based on that I got

Is this right so far?