Here is a site that clearly and thoroughly explains the graphs of the major mathematical functions. There are example problems solved, problems for the student to attempt, and answers to the student problems. Point this site out to...

A set of exercises of moderate difficulty on rational functions, complete with solutions and hints for students..

Students explore nonlinear inequalities. Graphs and detailed examples are included.

Trigonometry ratios and their signs are given in this explanation of the other trig functions. Graphs of tangent, cotangent, secant, and cosecant are given. Examples are included.