This is one exercise from Rudin's book,
Construct a continuous monotone function $f$ on $\mathbb{R}^1$ that is not constant on any segment but $f'(x)=0$ a.e.
This is one exercise from Rudin's book,
Construct a continuous monotone function $f$ on $\mathbb{R}^1$ that is not constant on any segment but $f'(x)=0$ a.e.