[Math] Real-valued function and extended-real-valued function, what’s the difference

functionsreal-analysis

This might be a simple question, but it is really confusing. I have not found any explicit definition or example of extended real-valued function.

My guess is that f defined by f: x -> 1/x on (0,1) is REAl-valued, while g defined by g: x -> 1/x on [0,1) is EXTENDED REAL-valued. Is this the case?

Could someone please give some examples?

Best Answer

In general, an $E$-valued function is a function that takes values in $E$.

The extended reals are $\mathbb{R}\cup\{\pm \infty\}$. So an extended-reals-valued function takes values that are either in $\mathbb{R}$, or possibly $\pm \infty$.

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