My maths isn't great, I've always found it interesting but I've never had more than a surface-level understanding of it. I managed to graduate with a computer science degree by learning just the mathematical concepts I needed for the task at hand and I quickly forgot most of what I learned after the exams were over. I've worked as a backend web developer ever since, which isn't an field that calls for much in the way of mathematics beyond the basics.I've recently been getting deeper into interests where this lack of a mathematical background is becoming a bit of a problem. I've been interested in machine learning concepts for a while so I looked into linear algebra, I've been interested in signal processing in music so I looked into things like Fourier transforms, the list goes on and I keep running into issues with my poor fundamentals. I just don't have a solid enough background with subjects like trigonometry and calculus to understand a lot of what's going on in many cases, I can kind of mentally "bodge" things together sometimes but it's a very inelegant way of going about it.What I have found quite useful is the kind of tutorials where concepts are given a visual, geometric interpretation which is quite strange as I'm not usually a particularly visual person. I'm still running into issues with my fundamentals though, so I guess my question is: assuming nothing more than mostly-forgotten A-level maths how can somebody who works full time build up a solid mathematical foundation so that they can progress to more advanced topics?Thanks in advance.