# Mathematica:How can I acclaim a variable is real in a complex function

by palzle
Tags: acclaim, complex, function, mathematicahow, real, variable
 P: 2 Hi,I'm a beginner. here's the example: f[x_] := E^(I*x) Conjugate[f[x]]*f[x] I'd like get 1,but it give me a complex function coz it regard x as complex. please help me:how to claim x is real? by the way,is that necessary to define a letter as a constant.no matter yes or not,how to refer a letter constant to be real or pure imaginary Thank you!
 Sci Advisor HW Helper P: 3,680 You could do f[x_]:=Exp[I*Re[x]] so it takes only the real part of x (which doesn't change it, of course, when x is real).
 P: 2 Thanks for your reply. I tried your answer,and it works. Well,I have some...eerr... what if I'd define the domain for function f[x]? I mean that I wanna prescribe x in f[x] must be real or pure imaginary or rational number.How to do that. I've a similar question here.How to claim a letter constant to be real or pure imaginary or rational number? Waiting for your kindness.

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