I found Precalculus Mathematics In A Nutshell by Simmons to be extremely valuable (as someone who got so stressed out by my maths teachers in primary school tha

I found Precalculus Mathematics In A Nutshell by Simmons to be extremely valuable (as someone who got so stressed out by my maths teachers in primary school that I literally was not able to add up in my head until the age of 14). It teaches the concepts and cuts out all of the crap, but the diagrams and the clearly stated formulas make a lot of the implicit knowledge, explicit and extremely elucidating.