Originally Posted by

**emmv** I am studying electrical engineering at university level in the UK. As part of a course on Circuit and Signal processing I have tutorial sheets on Fourier Analysis.

I am fine with fourier analysis except when I start to look at exponential fourier series, I have the question, I even have the answers and how the tutor reached the answer (the workings). But I am not understanding how he is jumping from one line to another. I have attached the whole solution but the bit that I am misunderstanding is:

$\displaystyle

r_{m}=\frac{-V}{4\pi^2}\displaystyle\{\frac{-1}{jm}[2\pi]\displaystyle\}$

$\displaystyle

\\r_{m}=\frac{-jV}{4m\pi^2}\{[2\pi]\}

$

where j = complex number $\displaystyle j^2=-1$, how is j moving from the denominator to the numerator?

surely the next line should be

$\displaystyle

\\r_{m}=\frac{V}{j4m\pi^2}\displaystyle\{[2\pi]\displaystyle\}

$

Any help would be greatly appreciated. Thanks Ed.