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If I have an expression, let us say something like this:

Cos[3 x] + π/cofe Exp[y^(c  z)]

how can I get all non-number symbols in the expression which are:

{x, cofe, y, c, z}

I tried this:

Cases[Cos[3 x] + π/cofe Exp[y^(c  z)], _Symbol]

but it didn't work.

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marked as duplicate by Mr.Wizard Jun 6 at 1:10

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1  
Possible duplicate: Is there an analogue of the Variables command for general expressions?. In short, does this do what you want?: Variables @ Level[expr, {-1}] (where expr is your expression). –  Mr.Wizard Jun 5 at 8:02
    
@Mr.Wizard thank you. this is what I am looking for. –  Algohi Jun 5 at 15:47

1 Answer 1

up vote 9 down vote accepted
expr = Cos[3 x] + \[Pi]/cofe Exp[y^(c z)];

Cases[expr, _Symbol?(! NumericQ[#] &), Infinity] // Union

(* {c, cofe, x, y, z} *)

In this case the Union is not necessary; however, in general it is needed to eliminate duplicates.

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This is a nice answer and I am puzzled there is no built-in for this sort of thing but Variables (for polynomial expressions) is the closest there is. (+1) –  gpap Jun 5 at 7:33
    
@Bob Hanion, thanks. this is nice answer. –  Algohi Jun 5 at 15:53
    
An alternative: Cases[expr, Except[_?NumericQ, _Symbol], ∞] // Union –  m_goldberg Jun 6 at 0:53

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