University of Colorado
University of Colorado: Exponential, Trigonometric and Hyperbolic Functions
This site explains the Exponential, Trigonometric and Hyperbolic functions
Other
Interactive Trigonometry
Resource contains interactive programs that can be manipulated and animation to help students grasp basic concepts in trigonometry.
Math Bits
Math Bits Notebook: Sine & Cosine of Complementary Angles
Provides theorems and examples relating to the sine and cosine of complementary angles.
CK-12 Foundation
Ck 12: Exact Values for Inverse Sine, Cosine, and Tangent
[Free Registration/Login may be required to access all resource tools.] Find all angles on the unit circle matching exact trig ratios. Resource includes examples, videos, and practice problems.
Purple Math
Purplemath: The Unit Circle
Relates the unit circle to the method for finding trig ratios in any of the four quadrants. Demonstrates how the unit circle might be useful.
University of Regina (Canada)
Univeristy of Regina: Math Central: Tangent Lines and Circle Equations
This site offers a problem and solution to finding all possible slopes for a line tangent to a circle given a particular equation of a circle. Could be an interesting challenge for students.
Other
Trigonometry: A Quick Review
This site is a personal site from David Eisenberg and it contains brief but great review information for trigonometry. This particular site focuses on sine and cosine inlcuding a small circle graph. Clicking on the index link provides...