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Finding real part of an expression. 
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#1
Dec912, 07:30 AM

P: 3,220

Hi, I have the next expression:
[tex] \frac{iw+3}{(iw3)(iw+6)(iw+1)}[/tex] Now I want to find the real part of this expression via mathematica or maple, and for the love of god it doesn't work, what have I done wrong here?! the codes and their errors are in the attachments. http://oi50.tinypic.com/25zs684.jpg http://oi50.tinypic.com/24wfqt3.jpg Peace out! N.B w is real parameter. 


#2
Dec912, 03:45 PM

P: 1,030

In[1]:= FullSimplify[Reduce[a+I b==(I w+3)/((I w3)(I w+6)(I w+1))&& a∈Reals&& b∈Reals&& w∈Reals,{a,b},Backsubstitution>True]]
Out[1]= w∈Reals && a == ((54 + 27*w^2 + w^4)/(324 + 369*w^2 + 46*w^4 + w^6)) && b == ((w*(27 + w^2))/(324 + 369*w^2 + 46*w^4 + w^6)) Check this result very carefully before you depend on it 


#3
Dec912, 09:56 PM

P: 3,220

Thanks. Who knew that such a simple task should have a long line of code?!



#4
Dec1112, 05:02 PM

PF Gold
P: 466

Finding real part of an expression.
What about "ComplexExpand"? ((Mathematica))
ComplexExpand[(I w + 3)/((I w  3) (I w + 6) (I w + 1))] [tex] \frac{27 w^2}{\left(w^2+1\right) \left(w^2+9\right) \left(w^2+36\right)}\frac{54}{\left(w^2+1\right) \left(w^2+9\right) \left(w^2+36\right)}\frac{w^4}{\left(w^2+1\right) \left(w^2+9\right) \left(w^2+36\right)}\\+i \left(\frac{27 w}{\left(w^2+1\right) \left(w^2+9\right) \left(w^2+36\right)}\frac{w^3}{\left(w^2+1\right) \left(w^2+9\right) \left(w^2+36\right)}\right) [/tex] 


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