Mathematics or, more precisely, trigonometry

came up in my internet conversations yesterday. 
Mm... I haven't used trigonometry since I left school. I did very little of it then. There was merely an introduction to the topic in our maths classes. 
Do you remember those little books we had? They were called "Logarithmic and other tables" but of course we called them "Bogarithmic and other fables". Most of my fellow students reworked the cover and title page to reflect this. I didn't dare. If I had done it my mother would have brought out the hair brush she used to hit us on our bare backsides. (She only stopped using it after it broke on my brother. He stood there, looked at her and then patted her on the head and said, "Little Mum". He was about fourteen at the time. I am two years older than he is.) 
But, back to the maths. I can, sort of, remember it but I would need to do a quick refresher course to actually solve a problem. I have actually never needed to find the height of a tree or a building which is about all I can really remember of those classes. 
Basic algebra on the other hand has been useful. I actually did a quadratic equation not that long ago.  Not everyone would need to do this and I can still remember the blank looks on the faces of my classmates as the Senior Cat started our first lesson. (This was long before "new maths".) How can a number be called "x" or "y"?
We were supposed to learn a lot of things in school that I could not see much point in. I saw no point in repeating the same "social studies" course each year. I wanted to learn more history, the Egyptians, the Romans, the Middle Ages, and much more. All I had  through primary school was the same old stories of explorers in our state and a little bit more of national history. When I should have had those things we moved and the curriculum in rural schools meant I had to repeat things I already knew. I read under the desk instead. I've forgotten a lot of the details of the stories of the explorers - but I have had to remind the Senior Cat of the order of succession in English history. I've forgotten most of my Latin and, later, my law. I remember a lot of psychology and linguistics - but I use those things all the time.
But the internet is there. If I search sensibly and use sites that should be reputable I can remind myself of all sorts of things - and I can learn new things all the time.
I still remember that first algebra lesson though. There was silence and then a young male voice asked,
   "Sir, how is this going to help me milk the cows?"
   "It isn't," the Senior Cat told him, "But you never know when it might turn out to be useful so you need to learn it."