I think real analysis is one of the boring math topics of engineering which sometimes becomes even more confusing when we try to just partially remember things(formulae, definitions) instead of imagining them. This math video is related to cauchy sequence of real analysis which describes the entire concept not just with the help of definition, but also with the help of a graph (which is always a life saver in understanding these boring topics) You can refer : http://mathonline.wikidot.com/cauchy-sequences-of-real-numbers It's subsequent video consists of a non-cauchy example.