Let $f:I\rightarrow\mathbb{R}$ be a continuous function which derivative exists a.e. and $\int f'$ exists in I. Also, suppose $f$ satisfies the Luzin N property. Show that $f$ is absolutely continuous.
So I don't seem to find any way to tackle this problem. This seems to be covered everywhere when the derivative is defined everywhere, but no such case when it's only a.e.
What I know is that using bounded variation it's possible to get absolute continuity, however I can't find how to prove the bounded variation condition.
Is there a reference or a way to solve this problem?
Answer
See 2. here. The theorem that's being proven assumes bv, but that condition is only used to establish that $f$ has a derivative a.e. that is integrable, which are exactly the conditions you have.
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