Check out these books for more information:
 Your high school math textbook will cover most of the material on functions and trigonometry.

The first chapters of most calculus books also offer a good review of functions and trigonometry. I use
Single Variable Calculus
by James Stewart
Brooks and Cole, January 2007 
Discrete Mathematics and Its Applications
by Kenneth H. Rosen
McGraw Hill, July 2006
This book is a really good introduction to many discrete mathematics topics such as logic, mathematical reasoning, modular arithmetic, and Boolean algebra. Highly recommended! 
A Concrete Introduction to Higher Algebra
by Lindsay N. Childs
Springer, December 2000
This book covers everything you need to know about modular arithmetic and its many applications.
This DriveBy material is licensed under a Creative Commons AttributionNoncommercialShare Alike 2.5 Canada License.