real analysis - Prove that a function whose derivative is bounded is uniformly continuous.

Suppose that $f$ is a real-valued function on $\Bbb R$ whose derivative exists at each point and is bounded. Prove that $f$ is uniformly continuous.

Answer

Since $f'$ is bounded then there's $M>0$ s.t.
$$|f'(x)|\leq M\quad \forall x\in\mathbb{R}$$
hence by mean value theorem we find
$$|f(x)-f(y)|\leq M|x-y|\quad \forall x,y\in\mathbb{R}$$
so $f$ is a lipschitzian function on $\mathbb{R}$ and therefore it's s uniformly continuous on $\mathbb{R}$.