Ok, I solved it.

I got f(0) =3. Is that right?

I then have another problem:

f(x) =definite integral from 0 to x:sin(t) / (t+1) dt.

1) Find where f(x) has local maximum and minimum values (I should not find the function values).

A more interesting one:

2) Show that f(x) > 0, when x > 0. (Here I should use integration by parts...)

Do anyone want to help? :-)