# Sigma Notation Cheat Sheet

I'm just over a quarter of the way through MST121: Using Mathematics, which I started back in September. My impression is that it's starting to get tougher, but it may just be that my mind has been elsewhere.

One concept with which I found myself to be less confident is Sigma Notation. The principle itself is fairly straightforward (it's kind of like a `for`

loop, if you ask me) but getting actual numbers out of the other side was another matter.

The problem was that I was consistently failing to spot the patterns that indicate that you can substitute in other, hopefully simpler, expressions. So I made a little *aide memoire* to print out. It covers the ~~three~~ four initial, erm, refactorings that have cropped up, and I figured I may as well share it.

The whole exercise also gave me an excuse to get to grips with typesetting mathematical expressions in the rather wonderful LaTeX. I've a fair bit to learn, so if anyone who's stronger than me at maths and/or LaTeX fancies sending me any pointers, they'd be welcome.

The cheat sheet is available as:

I'll try to update this post when I find the right tool + inclination to make a nice PNG of it. But first I've a few more exercises to run through to see if this has even helped.