# Questions tagged [assumptions]

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### Why does Mathematica simplify $x/x\to1$?

If I enter x/x, I get 1. Such behavior leads to this: Simplify[D[Sqrt[x^2], x, x]] 0 ...
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### Is it possible to set a variable as a positive one in the whole notebook?

I'm having issues during integration due to the fact that Mathematica doesn't know if an undefined variable is positive or not (it gives me complexes which bothers me in the end). For example I do ...
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### Can't simplify Abs[a*Cos[x]]^2

Why doesn't FullSimplify[ Abs[a*Cos[x]]^2, Assumptions -> {{a, x} ∈ Reals}] simplify to (a*Cos[x])^2 but this query <...
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### Does the Im function work with symbolic arguments?

Does the Im function work with symbolic arguments? ...
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### Simplifying conditional expressions using assumptions does not work

I have a conditional expression f[x_] := x /; x ∈ Reals This works fine for normal numbers and symbols, e.g. ...
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### Replacements/Substitutions in Mathematica

I am a new user of Mathematica and have some questions about the simplifications of calculated expressions. I am unable to attach an image of the session, but my Mathematica commands are: ...
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### Why doesn't Abs simplify further?

Why does this: Simplify[Abs[x + I], Element[x, Reals]] give me Abs[x + i] Is there a way to force Mathematica to give me ...
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### Assumptions on unknown functions

I'm trying to do analytic calculations in a quantum mechanic harmonic oscillator basis. Specifically I want to be able to evaluate functions of the many particle density. I define the following ...
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### Conjugating symbolic expression [duplicate]

I am trying to conjugate a symbolic expression, and I have explicitly stated the real terms. However, I simply can't get it to work: ...
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### Inconsistent results for equivalent converging symbolic integrals

Bug introduced in 9.0 or earlier and persisting through 11.0.1 or later I have looked at previous questions and I'm aware that this seems to be a known bug: Mathematica giving inconsistent results ...
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### Detecting operator Set in Assumptions

Here is a typical issue: Simplify[x + y, x = y] produces 2 True. Is there a way to detect operator ...
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### Simplify with assumption of unknown function [duplicate]

I have an unknown multivariate function entry[x,y,z], which is positive. Then how to get FALSE and entry[1,2,3] in the following evaluations? ...
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### FullSimplify a trigonometric expression doesn't work as expected

I know this kind of question is frequent asked, yet each case has its own particularities. I will show my problem. I define the following: ...