I am currently in High School, possibly interested in pursuing a career in Mathematics or the Philosophy/Logic behind Mathematics. I don't have a lot of money for books or videos about Higher Mathematics, but I have been using Wikipedia to learn Maths.
I don't understand why nothing can be as concise and beautiful as Wikipedia. When we learned about functions in school, my teacher took an entire class just to explain them to us. He kept trying to use visuals and all these different tools to explain what a function is, and then, mildly confused, I looked up "function" on Wikipedia, and here is the definition I get:
In mathematics, a function is a relation between a set of inputs and a set of permissible outputs with the property that each input is related to exactly one output.
I would much rather use Wikipedia to learn Mathematics, because of how concise it is. Sometimes I don't want to know every single thing about a function, I just want a sufficient definition.
Is there any encyclopedia or book that will have definitions and teach you Mathematics in this way? I'm not trying to sound egotistic. I am just a very fast learner and I would much rather blaze through a paragraph that explains things very concisely than spend hours learning the same material in different ways. Is Wikipedia good for learning Mathematics, or is there an alternative way to concisely learn what I want to know?