How to extract real and imag part from symbolic expression

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Ivan 2019-10-27

评论： Walter Roberson 2019-10-28

Hi,

I have the following symbolic expression:

a=((6*pi*a0)/(6*pi-j*(kn^3*a0)));

ap=a/(1-a/(16*pi*R^3)*((eps_s-eps_w)/(eps_s+eps_w)));

all parametrs are difined as a real.

when I type real(ap) or imag(ap) it can not extract these parts. What could be the solution of this problem?

Thx

Ivan 2019-10-27

No, j is here written as an imaginary unit, sqrt(-1).

Walter Roberson 2019-10-28

You are right, MATLAB has difficulty finding those components.

Walter Roberson 2019-10-28

simplify( expand( real(ap) ) )
simplify( expand( imag(ap) ) )

Ivan 2019-10-28

I have tried out already. It still does not work properly.

In general, I was surprised that Matlab is weak to calculate such simple expressions.

Do you have maybe other ideas about how to overcome this problem?

Walter Roberson 2019-10-28

What do you mean by "it still does not work properly" ?

I did not check every term, but the results look to be the same as what I obtained using Maple .

There does not appear to be any simple form for the expressions.

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