# Simplifying complex expressions

I'm trying to work with complexes and I want Mathematica to know that all variables are real unless I explicitly assigned the variable with an I so I wrote:

$Assumptions = Except[I,_] ∈ Reals  It worked fine for simple expressions f = Exp[-I*a] * a + Exp[-I*b] Simplify[Conjugate[f]]  Exp[I*a] * a + Exp[I*b] but for a more complex expression: g = Exp[-I*a] * a + Exp[-I*b] * b Simplify[Conjugate[g]]  Exp[-I*a] * a + Exp[-I*b] * b which is wrong. What can I do about it? - ## 1 Answer You cannot use Except in$Assumptions like you do.
Just use ComplexExpand which assumes that are variables are real. E.g.:

conj = TrigToExp@ComplexExpand@Conjugate@# &;


Then

  conj[ Exp[-I*a]*a + Exp[-I*b]*b ]


gives

  a*E^(I*a) + b*E^(I*b)

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