# How to best add assumption that many variables are positive?

I often need to check whether integrals are solvable in closed form and use a notebook with 5–10 variables that need to be assumed positive. Is there a better way of doing this than adding the clunky line:

$Assumptions=a>0&&b>0&&c>0&&d>0&&f>0; ? I tried $Assumptions={a,b,c,d,f}>0; but it didn't work.

• $Assumptions=Thread[{a,b,c,d,f}>0]? – kglr Apr 24 '20 at 13:56 • also $Assumptions=Element[{a,b,c,d,f}, PositiveReals]
– kglr
Apr 24 '20 at 13:57
• @kglr Both worked! Thanks. Apr 24 '20 at 13:59

$Assumptions = Element[{a, b, c, d, f}, PositiveReals] ; Simplify[Sign[a + b + c]]   1  $Assumptions = {};
Simplify[Sign[a + b + c]]

 Sign[a + b + c]

$Assumptions = Thread[{a, b, c, d, f} > 0] ; Simplify[Sign[a + b + c]]   1  $Assumptions = AllTrue[{a,b,c,d,f}, Positive] ;
Simplify[Sign[a+b+c]]

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