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Mathematics Algebra Wolfram Language

Simplify the FractionalPart of an expression including variables

Hongyi Zhao

Posted 1 year ago

See my following testing: In[199]:= Assuming[{n1,n2,n3}\[Epsilon] Integers, FractionalPart[n1 + 2 n2 - 3 n3 ]] FullSimplify[FractionalPart[n1 + 2 n2 - 3 n3], {n1,n2,n3}\[Epsilon] Integers ] Out[199]= FractionalPart[n1 + 2 n2 - 3 n3] Out[200]= FractionalPart[n1 + 2 n2 - 3 n3] Why can't I simplify the results, that is, return the correct results 0? Regards, Zhao

See my following testing:

In[199]:= Assuming[{n1,n2,n3}\[Epsilon] Integers, FractionalPart[n1 + 2 n2 - 3 n3 ]]
FullSimplify[FractionalPart[n1 + 2 n2 - 3 n3], {n1,n2,n3}\[Epsilon] Integers ]

Out[199]= FractionalPart[n1 + 2 n2 - 3 n3]

Out[200]= FractionalPart[n1 + 2 n2 - 3 n3]

Why can't I simplify the results, that is, return the correct results 0?

Regards, Zhao

POSTED BY: Hongyi Zhao

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Hans Milton

Posted 1 year ago

`Assuming` does not affect evaluation of every type of its second argument. Its scope is limited. From documentation: In[23]:= Assuming[Element[{n1, n2, n3}, Integers], FractionalPart[n1 + 2 n2 - 3 n3] // Simplify] Out[23]= 0 Or: In[25]:= Assuming[Element[_Symbol, Integers], FractionalPart[n1 + 2 n2 - 3 n3] // Simplify] Out[25]= 0

Assuming does not affect evaluation of every type of its second argument. Its scope is limited. From documentation:

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In[23]:= Assuming[Element[{n1, n2, n3}, Integers], FractionalPart[n1 + 2 n2 - 3 n3] // Simplify]

Out[23]= 0

Or:

In[25]:= Assuming[Element[_Symbol, Integers], FractionalPart[n1 + 2 n2 - 3 n3] // Simplify]

Out[25]= 0

POSTED BY: Hans Milton

Hongyi Zhao

Posted 1 year ago

In[5]:= Assuming[Element[{n1, n2, n3}, Integers], FractionalPart[n1 + 2 n2 - 3 n3 ]] Simplify[FractionalPart[n1 + 2 n2 - 3 n3], Element[{n1, n2, n3}, Integers]] Out[5]= FractionalPart[n1 + 2 n2 - 3 n3] Out[6]= 0 Why does the "Assuming" approach not work? You have used the infix form [Epsilon], it should be [Element]. Thank you for pointing out my misuse of mathematical symbols. The shapes of these two symbols are so similar that I really didn't notice their differences.

POSTED BY: Hongyi Zhao

Hans Milton

Posted 1 year ago

In[13]:= Simplify[FractionalPart[n1 + 2 n2 - 3 n3], Element[{n1, n2, n3}, Integers]] Out[13]= 0 You have used the infix form `\[Epsilon]`, it should be `\[Element]`.

POSTED BY: Hans Milton

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