Assuming and Conjugate do not work as expected

Asked Nov 08 '16 at 22:43

Active Nov 09 '16 at 00:39

Viewed 38 times

I tried to work with Conjugates in Mathematica and it did not produce my desired result. I learned about assumptions and figured they're my way to go. This is the code:

Assuming[Element[a, Reals] && Element[e, Reals] && Element[m, Reals] && 
Element[r, Reals] && e > 0 && r > 0 && m > 0, Conjugate[(a E^(-I Sqrt[2] Sqrt[e m] r))/r]]

However, this is the output:

(E^(I Sqrt[2] Conjugate[Sqrt[e m] r]) Conjugate[a])/Conjugate[r]

Since all variables are real and positive, I'd expect only the sign in the exponent to flip. Why does it still want to conjugate real positive variables?

edited Nov 09 '16 at 00:39

m_goldberg

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asked Nov 08 '16 at 22:43

infinitezero

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Documentation for Assuming states clearly that it automates passing its argument to $Assumptions, to be used by functions that have the Assumptions option. Conjugate is not such a function. But Simplify is such a function so you might try wrapping that around the expression to be altered. – Daniel Lichtblau Nov 08 '16 at 23:12
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Also see this prior MSE thread or this one – Daniel Lichtblau Nov 08 '16 at 23:14
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This is similar to several other question - the closest I could find is this: Replacements/Substitutions in Mathematica – Jens Nov 08 '16 at 23:22
@infinitezero, you might be interested in this "cheat sheet" I made for my complex analysis students: https://github.com/rljacobson/Complex-Analysis-with-Computer-Algebra. – Robert Jacobson Jun 13 '19 at 02:31

Assuming and Conjugate do not work as expected

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