I have begun to read about the hyperreals, and am wondering whether the natural extensions of real-valued functions to hyperreal-valued functions is simply a definition of the hyperreals, or can it be proved? Or is it accepted as an axiom?(adsbygoogle = window.adsbygoogle || []).push({});

For example, if f(x) = sin(x), then is the existence of f*(x) = sin*(x) provable, or is it assumed? (f*(x) and sin*(x) represent the natural extensions.)

Thanks!

BiP

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# Can the existence of nonstandard hyperreal extensions be proved?

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