CK-12 Foundation
Ck 12: Trigonometry: Double Angle Identities
[Free Registration/Login may be required to access all resource tools.] Derivation of double angle identities for sine, cosine, and tangent.
CK-12 Foundation
Ck 12: Trigonometry: Pythagorean Identities
[Free Registration/Login may be required to access all resource tools.] Defining trigonometric identities that rely on the Pythagorean Theorem.
Other
Dans Math: Lessons: Trigonometry
College professor Dan Bach reviews basic trig concepts, including trig functions, right triangles, circles, radians, and polar coordinates. Site includes animated graphs and detailed examples.
CK-12 Foundation
Ck 12: Geometry: Inverse Trigonometric Ratios
[Free Registration/Login may be required to access all resource tools.] Use the inverse trigonometric ratios.
CK-12 Foundation
Ck 12: Trigonometry: Inverse Trigonometric Functions
[Free Registration/Login may be required to access all resource tools.] This lesson covers the inverses of all six trig functions.
Math Is Fun
Math Is Fun: Triangle Identities
View examples of triangle identities, equations that are true for all triangles: Law of Sines, Law of Cosines, and Law of Tangents. Follow links to learn more about the purpose and examples of each identity.
CK-12 Foundation
Ck 12: Flex Book: Trigonometry
[Free Registration/Login may be required to access all resource tools.] Six-chapter book that introduces students to trigonometry. Topics include right angles, circular functions, trigonometric identities, vectors, and polar equations.
Lawrence Hall of Science
The Math Page: Trigonometry: Trignometry of Right Triangles
Here is a site that clearly and thoroughly explains the trigonometry of a right triangle, including finding the values of all six trig functions given a single value. There are example problems solved, problems for the student to...
Cool Math
Coolmath: The Pythagorean Identities
One page reference sheet of a quick recall of the Pythagorean Identities.
Cool Math
Coolmath: Pre Calculus Other Identities to Know
One page reference sheet of a quick recall of the Trig Identities.
CK-12 Foundation
Ck 12: Trigonometry: Applications of Inverse Trigonometric Functions
[Free Registration/Login may be required to access all resource tools.] Here you'll learn how to apply inverse trig functions to solve problems you would see in real-life situations.
Government of Alberta
Learn Alberta: Math Interactives: Exploring Trig Ratios
Investigate the cosine, sine, and tangent ratios of trigonometry using this interactive Learn Alberta math resource. Students will use these ratios to determine a right triangle's unknown side or angle. Be sure to follow the link to the...
Clark University
Clark University: Dave's Short Trig Course
This Clark University trigonometry tutorial site features questions and answers about what students can learn from trigonometry.
Wolfram Research
Wolfram Math World: Double Angle Formulas
Part of Eric Weisstein's comprehensive math site, this page deals with double-angle formulas. This site includes traditional trigonomic double-angle functions as well as hyperbolic trigonometric function. Includes links to related terms...
CK-12 Foundation
Ck 12: Trigonometry: Sine, Cosine, and Tangent Functions
[Free Registration/Login may be required to access all resource tools.] This lesson covers the three trigonometric ratios: sine, cosine, and tangent.
CK-12 Foundation
Ck 12: Trigonometry: Triple Angle Formulas and Linear Combinations
[Free Registration/Login may be required to access all resource tools.] Advanced applications of trigonometric identities.
Math2
Math2.org: Trigonometry Functions
A complete look at trig functions. From an "overview," page giving general definitions and important vocab words, to a listing of the 12 trig functions, to an explanation of the three modes used in trigonometry, to the procedures of how...
CK-12 Foundation
Ck 12: Trigonometry: Cofunction Identities and Reflection
[Free Registration/Login may be required to access all resource tools.] Find different trigonometric functions that have the same values for a given angle.
Khan Academy
Khan Academy: Find Trig Values Using Angle Addition Identities
Find the trigonometric values of various angles that (while they are not special angles) can be expressed as the sum or difference of special angles. Students receive immediate feedback and have the opportunity to try questions...
Khan Academy
Khan Academy: Using the Trig Angle Addition Identities
Find the trig values of sums of angles whose individual trig values are known. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
CK-12 Foundation
Ck 12: Trigonometry: Sine Sum and Difference Formulas
[Free Registration/Login may be required to access all resource tools.] Sine of a sum or difference related to a set of cosine and sine functions. Here you'll learn to rewrite sine functions with addition or subtraction in their...
CK-12 Foundation
Ck 12: Trigonometry: Cosine Sum and Difference Formulas
[Free Registration/Login may be required to access all resource tools.] Examples, videos, and practice problems covering cosine of a sum or difference related to a set of cosine and sine functions. Here you'll learn to rewrite cosine...
Purple Math
Purplemath: Using Identities to Evaluate
Demonstrates how to evaluate trigonometric functions by using trig identities.
Khan Academy
Khan Academy: Solving for a Side in Right Triangles With Trigonometry
Learn how to use trig functions to find an unknown side length in a right triangle.