Question: How can I set the domain and the codomain of my x?

I'm pretty new here, in maple and I think I'm not very good in math too but I would like to discover how to limit or set the domain of my x. Example: sin(x); I would like to set the type of the x to N (natural) and the type resulting to R (real). But after hours and hours of searches on google I subscribed to ask this to you, gentlemen :P Thank you everyone
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