# Problem with the product of complex numbers

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Hello,

I calculated the equivalent impedance of an RLC circuit, and I would like this one to be completely resistive (complex part equals to 0). So I declared my variables as 'syms' and I used the function 'solve' to obtain the equivalent impedance litterally like:

% syms R X Y Z

% Zeq=solve('(R+i*X)*(-i*Y)/(R+i*X-i*Y)=Z',Z)

The problem is that Matlab gives me a solution like this:

%Zeq =

% -(Y*(R + X*i)*i)/(R + X*i - Y*i)

But I would like something like: Zeq = A + i*B.

Could anyone help?

Thanks

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### More Answers (1)

Walter Roberson
on 24 May 2013

You cannot do that unless you add the assumption that the variables are real-valued

syms R X Y Z real

Zeq = simplify(solve((R+i*X)*(-i*Y)/(R+i*X-i*Y)-(Z),Z));

A = simplify(real(Zeq));

B = simplify(imag(Zeq));

A + B*i

##### 8 Comments

Walter Roberson
on 25 May 2013

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