Hence, my reason for prepending "relatively" before "easy" :) I admit the Fourier series part probably isn't standard knowledge. On the other hand, every student of a science-related field has (hopefully!!) at least taken calc one, so should be familiar with the rectangle rule for approximating integrals.

Hum wasn't taught in my calc 1 class. I know what DFT is and studied a lot more calc but I didn't get that until at least cal2 when we started working with integrals regularly.

We did, and yes, we learnt the thing you're mentioning. I however, had absolutely no idea what it was called anymore. But thanks for the links, I now remember.