Linear Algebra is so cool

I took Linear Algebra at like... 3rd semester of chemical engineering.

I found it was incredibly useful and had the tools to do quite cool stuff with all that diagonalization and matrix functions. It seemed much more powerful than just escalar or vectorial functions.
Then in all the following courses I took there was almost no use for it, I've forgotten most of what I've learned for lack of practice.

I loved that thing about rotating the reference axis to get a simpler expression of a function in a new system. Cool stuff.