This is a proof my teacher wanted us to do, but when coming to giving the solution, he got confused (Worried)
The problem is :
Where is 'the negative part of the function' :
Also, is a sequence of measurable functions, but I'm not sure it intervenes here.
As a sidenote, this was used in a proof of the generalization of Beppo-Levi's lemma.
Thanks in advance !