- #1
diddy_kaufen
- 7
- 0
Homework Statement
Find a function in a measurable space that is non-measurable, but |f| and f2 are measurable.
Homework Equations
None.
The Attempt at a Solution
I am trying to understand the following answer to the problem:
(source: http://math.stackexchange.com/a/1233792/413398)
I do not understand why for all subsets [itex]S \subseteq \mathbb{R}[/itex], we have $$(|f|)^{-1}(S)=(f^2)^{-1}(S)=X \text{ or } \varnothing$$