Your question, as you might guess, depends on where you are mathematically and how deep you want to go. A reasonable beginning (and affordable, too) is one of the Schaum's Outline series on Caluculus, Trigonometry. A far better and harder to find option is Edwin Moise's (out of print) book entitled something like Calculus. You should be able to find a reference on Amazon or Barnes & Noble or whatever. Another good source is Springer-Verlag and Dover Publications (less expensive). Hope this helps.