Does math have to be learned linearly? I am asking because often times one doesn't know where to start in math. "Just learn what you need" is very vague and unspecific ... for example, assume I'm a beginner at Algebra and was considering 3-D programming with OpenGL and C++. Not bothering to mention anything programming specific here, let's assume I must know vector math.
Does that mean:
1.go straight to vector math tutorials/books/etc. and learn it;
2.learn whatever prerequisites are recommended before vector math/linear algebra;
3.do something else.
Basically, what if I go straight to vector math and "don't get it"? Then what? Do I just linearly learn it or patch up some misinformation? Would I be learning vector math if I haven't even completed Algebra I yet? A little muddled on some Pre-Algebra as well?
Basically, again, at this point what is one expected to do? Do I need to learn it all from the bottom up or can I just "pick what I want" and learn it without caring about prior subjects fully or future ones?
 A: For ANY subject (whether Linear Algebra, Quantum Mechanics, or 19th century French literature), there are certain pre-reqs that MUST be known before you will be able to learn it at all.  For instance, trying to learn quantum mechanics without knowing some basic Hamiltonian mechanics will not be possible, because the modern interpretation of QM is based on something called the Hamiltonian of a system.That said, there is usually not one set of pre-reqs that every book and every teacher will assume.  Generally you can start learning a subject (like "vector math") from any of several different sets of pre-reqs.  Because though, you MUST know some elementary algebra, like the quadratic formula and factoring and such, you may or may not need some Euclidean geometry, trigonometry (actually you probably would need this one), or basic calculus to start learning, depending on what source you're going to use to learn it.
If you want an answer more specific to you, you'll need to let us know exactly what math you do know.  Then I'm sure someone more familiar with 3D programming than myself can recommend some source, IF you know those basics of elementary algebra that you need.  If not, we can recommend sources for that, too.
