Math teachers have a love / hate relationship with Vi. On the one hand she has made lots of pretty awesome videos about Math-stuff. On the other, she almost always makes sure to bash math-education a little in her videos (it's boring, it's pointless, it's not taught well, etc.). Oh well, she does make some good points at times. And the videos are cool!
I'll post two videos here. The first one is her first math video ever. It looks a little grainy / low budget now, but it's the first one ever so I gotta show you that one. The second one is a more recent effort of Vi's. By the way, if you want (LOTS) more videos like these, click on the picture of Vi Hart above. It'll take you to her website. Happy exploring.