I have recently experienced a renewed interest in mathematics. I loved it as a young child and throughout the start of high school, but lost interest as my focus shifted to cars, girls, and college parties.
After perusing some pages on Mathworld at the Wolfram Research website and feeling quite bewildered, I felt so relieved when I came upon the page for the identity matrix.
I have long since remembered matrices and how they are built, but my recent and relatively often use of identity transforms in XSLT which made the identity matrix so familiar.
In my understanding, identity transforms can perform a transformation on an input XML document and produce the output XML which is the same as the input XML.
The concept is similar with the identity matrix. A matrix which is multiplied by an identity matrix produces an outcome identical to the original, non-identity matrix.
Perhaps I am dull, but I think this is cool stuff.