There's no such thing as "learning mathematical notation". You learn whatever field you are interested in, and the text you are reading will tell you what the n

There's no such thing as "learning mathematical notation". You learn whatever field you are interested in, and the text you are reading will tell you what the notation is, as "we'll denote multiplication of `a` and `b` by `ab`", "we'll denote `A` implies `B` by `A => B`", "we'll denote derivation of `f` wrt `x` with `df/dx`", etc.