About
My name is Dan Boykis and I enjoy thinking about mathematics, physics and computer science or just anything that catches my fancy. Every post I write is interesting to me in some way. To me blogging is a selfish activity, I do it to form more complete and thorough thoughts on a subject I am writing about. If as a consequence what I write is useful to you the reader than all the better!
October 17th, 2011 - 07:00
I was looking through your derivation of sums of squares and found some things that I don’t yet understand. I’d like your help in understanding some of it…
Please refer to this website http://danboykis.com/2009/03/derivation-for-sum-of-squares/ Starting just after where it says “Here’s the derivation:” I can follow the first line of symbols. I can also understand how you get from the first step in the 2nd line to the next step in the 2nd line. However I don’t understand how you go from the second step to the 3rd step in the second line. Is this an identity of some sort? Or is this “common knowledge” when doing “sigma math”?
Please help!