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Igor
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Symbolic Math Toolbox VS MuPAD: example in advance of the first?

Asked by Igor
on 6 Jun 2011
MATLAB
>> simplify(exp(log10(x)))
ans =
x^(1/log(10))
MuPAD
simplify(exp(log(10,x)), ln)
No effect. How to force MuPAD to simplify truely? I used consider MATLAB Simb.Tbx as a reduced version of MuPAD? That is -- MATLAB calls the MuPAD functions...

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3 Answers

Answer by Walter Roberson
on 7 Jun 2011
 Accepted Answer

This is as documented here
Mathematically, log(b, b^y) = y holds true for any real y. This simplification is implemented for the following cases: i) b is a symbolic (indexed) identifier and y is of type Type::Real, ii) b is numerical and y is integer or rational.
and
Note that arithmetical rules such as log(b, x*y) = log(b, x) + log(b, y) are not valid throughout the complex plane. Use properties to mark identifiers as real and apply functions such as expand or simplify to manipulate expressions involving log. Cf. example 4.
So you could possibly use
simplify(exp(log(10,x))) assuming x::real

  2 Comments

Might have to be x::Real perhaps, instead of x::real
Clearly.
But Log of complex value may be account like sin() with periodic term.
Thanks.

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Answer by Paulo Silva
on 6 Jun 2011

syms x
simplify(exp(log10(x)))

  1 Comment

No, no :)
MATLAB works validly, you haven't seen ANS
Problem in MuPAD

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Answer by Andrei Bobrov
on 6 Jun 2011

in MuPAD
expand(subs(exp(log(10,x)),log(10,x)=ln(x)/ln(10)));
EDIT
rewrite(exp(log(10,x)),ln)

  1 Comment

the last better..
thanks

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