Hello I am trying to find the $D_n$ coefficient for the given square wave using complex exponentials.
$$D_n = \frac{1}{4}[\int_{1}^{3}(-1)e^{\frac{-jn \pi t}{2}}dt + \int_{3}^{5}(1)e^{\frac{-jn \pi t}{2}}dt ]$$ Afterward I get the following which is simplified to the best of my with skipping a couple of steps
$$D_n = \frac{1}{2jn \pi}[2e^{\frac{-3nj \pi}{2}} - e^{\frac{-nj \pi}{2}} - e^{\frac{-5nj \pi}{2}}]$$
I was wondering if this expression could be simplified further, thanks in advance