
Horizontal Tangent
Alright guys so I need someone to explain to me how to find the horizontal tangent for this question but in general I need to know it.
For what values of x does the graph of f have a horizontal tangent? (Use n as your integer variable. Enter your answers as a commaseparated list.)
f(x) = x+ 2 sin x
So I know the derivative is 1 + cosx I believe so what's the next step?

Re: Horizontal Tangent
You forgot the constant "2", derivative should be f'(x) = 1 + 2 cos x.
f has a horizontal tangent when f'(x) = 0.

Re: Horizontal Tangent
Ooh, but how do you find the horizontal tangent once you get the derivative? Or if it's 0 wouldn't the HT just be 1.

Re: Horizontal Tangent
You know what the derivative is, you want to set it to zero, why not set 1 + 2 cos x = 0?