Dear Gianluca Gorni,
Many thanks for your help. Now, I'm trying to apply the same manner that you explained above but in different problem. I don't get expected answer from Mathematica.
Here is the code:
In[1]:= Quit[]
In[1]:= ClearAll;
EE = Solve[[Sigma]y == D[p x y^3 - 2 p x^3 y, y], [Sigma]y]
In[3]:= Solve[[Tau]xy ==
D[-1.5 p x^2 y^2 + c1 y^2 + .5 p x^4 + c3, x], [Tau]xy]
In[2]:= Solve[[Tau]xy ==
D[-1.5 p x^2 y^2 + c1 y^2 + .5 p x^4 + c3, x], [Tau]xy] /. EE
Out[2]= {{[Tau]xy -> 2. p x^3 - 3. p x y^2}} /. EE
As you see in the Out[2], I want the answer to be in terms of [segma]y.
Can you please tell me the right code in this case? I attached the file too.
Thank you
Attachments: