Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

Rudin-RCA p.15

Let $X$ be a measurable space. Let $\{f_n\}$ be a sequence of extended-real measurable functions on $X$.

How do i prove that $\sup_n f_n$ is measurable?

Rudin uses a criterion to prove this, that is, if for every real $\alpha$, $f((\alpha,\infty])$ is measurable, then $f$ is measurable.

I don't understand why this is sufficient to prove this.. Help me

share|improve this question
3  
I just proved it, sorry for disturbing.. –  Katlus Jan 9 '13 at 1:06
2  
You can answer your own question and even accept your own answer so the question doesn't go unanswered in the system. –  Clayton Jan 9 '13 at 1:18
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.