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When I evaluate:

Assuming[3 > jj >= 1 && jj \[Element] Integers, 
 ThreeJSymbol[{jj, 0}, {1, 0}, {2, 0}]]

it outputs an expression saying that if

$3 > jj \ge 1$

I get a nonzero answer, otherwise it's zero. How do I remove this conditional? I found that Simplify does the trick, but this expression appears in a much bigger expression that I don't want to Simplify, because it will take forever. Is there a quick way to remove the conditional?

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  • $\begingroup$ The Simplify should be placed within the scope of the Assuming, i.e., Assuming[3 > jj >= 1 && jj \[Element] Integers, ThreeJSymbol[{jj, 0}, {1, 0}, {2, 0}] // Simplify] You can use parentheses to restrict the scope of the Simplify $\endgroup$
    – Bob Hanlon
    Commented Sep 30, 2022 at 22:00
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    $\begingroup$ Hi, I think you need to provide mory information, otherwise one has to guess what your actual expressions look like and how they were generated. You could try yourExpression /. {f_Piecewise :> Simplify[f,Assumptions -> yourAssumptions]}. $\endgroup$
    – user293787
    Commented Oct 1, 2022 at 2:36
  • $\begingroup$ Here is a related post. $\endgroup$
    – user293787
    Commented Oct 1, 2022 at 3:59

1 Answer 1

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Does this meet your needs?

expr = ThreeJSymbol[{jj, 0}, {1, 0}, {2, 0}];
Extract[expr, {1, 1, 1}]
expr[[1, 1, 1]]

enter image description here

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