Purple Math
Purplemath: Angles of Inclination and Declination
Explains the terminology for angles of elevation, depression, inclination, and declination. Demonstrates how to 'translate' exercises into triangles and equations.
Purple Math
Purplemath: Proving Trigonometric Identities
An "identity" is a tautology, an equation or statement that is always true, no matter what. Proving an identity is very different in concept from solving an equation. This resource demonstrates some useful techniques for proving...
Purple Math
Purplemath: Quadrants and Angles
Explains how to model angles in the x,y-plane, and demonstrates how to extend the concept of trig ratios to angles larger than 90 degrees.
Purple Math
Purplemath: Using Identities to Evaluate
Demonstrates how to evaluate trigonometric functions by using trig identities.
Purple Math
Purplemath: Trigonometric Identities
Lists the basic trigonometric identities, and specifies the set of trig identities to keep track of, as being the most useful ones for calculus.
Purple Math
Purplemath: Right Triangle Word Problems
Demonstrates how to translate, set up, and solve basic right-triangle word 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.