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Mathematica 10.0, having problems simplifying simple expressions.

Posted 10 years ago

Basically my mathematica can't simplify a simple expression, enter image description here

DVP can be simplified to sqrt(amh) , which is what I would expect mathematica would give me, (I tried the other functions as well, ''Cancel'', ''Expand'',etc), but I just get the same solution that doesn't look simplified at all,

help me plz :D.

5 Replies
Posted 10 years ago

Here's what I get when giving some assumptions. Otherwise Mathematica must give results which are generally valid.

In[1]:= dvp = Sqrt[(Sqrt[(a m)/h^5] Sqrt[a h m])/h];

In[2]:= Simplify[dvp]

Out[2]= Sqrt[(a m Sqrt[(a m)/h^5])/Sqrt[a h m]]

In[3]:= Simplify[dvp, Assumptions -> Element[_, Reals]]

Out[3]= Sqrt[a m]/Abs[h]^(3/2)

In[4]:= Simplify[dvp, Assumptions -> {Element[_, Reals], h > 0}]

Out[4]= Sqrt[(a m)/h^3]
POSTED BY: David Keith

Dear Tigran,

I think that the problem is that the expression does not simplify the way you think it simplifies without making additional assumptions. You need to consider cases when the variables are negative or complex numbers etc.

I suppose that something similar to what you want happens when you make for example the following assumptions:

Simplify[Sqrt[(Sqrt[(a m)/h^5] Sqrt[a h m])/h], Assumptions -> {a > 0, m > 0, h > 0}]

That gives

enter image description here

This is different from what you expect, but I think that you might have made a mistake there in your calculation. An alternative set of assumptions could be:

Simplify[Sqrt[(Sqrt[(a m)/h^5] Sqrt[a h m])/h], Assumptions -> {a \[Element] Reals, m \[Element] Reals, h \[Element] Reals}]

or equivalently

Simplify[Sqrt[(Sqrt[(a m)/h^5] Sqrt[a h m])/h], Assumptions -> {{a, m, h} \[Element] Reals}]

both of which give

enter image description here

Hope this helps,


POSTED BY: Marco Thiel

Hi David,

sorry, your reply came in just before mine... I had not seen it before submitting.



POSTED BY: Marco Thiel
Posted 10 years ago

Hi Marco,

In this case, more is better. And I think your reply is more informative.

Kind regards, David

POSTED BY: David Keith

Thx guys, using assumptions worked :)

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