The question.
Let $f$ be a differentiable map $\mathbb R_+\to\mathbb R$ such that
$\forall x\geqslant0,\quad f'>0$
$\exists M>0,\quad \forall x\geqslant0,\quad f(x)\leqslant M$.
Does there exist $f$ verifying such conditions such that $f'(x)$ does not tend to $0$ when $x$ goes to infinity?
What I tried.
I think the answer is yes because of the following.
I tought about a function $f'$ doing something resembling to $x\mapsto \frac 1{1+x^2}$, but with little peaks like this:
This function would not have a limit when $x\to\infty$, and $f$ would still be bounded.
Final questions.
Does this idea works? Can you formalise it? Am I totally wrong here?