Trigonometric Identities
These lessons, with videos, examples and step-by-step solutions, help High School Algebra 2 students learn about trigonometric identities.
Related Pages
Trigonometric Graphs
Lessons On Trigonometry
Trigonometric Functions
More Algebra II Lessons
Math Worksheets
Trigonometric Identities:
Identities are equations true for any value of the variable.
Since a right triangle drawn in the unit circle has a hypotenuse of length 1, we define the
trigonometric identities x = cos(theta) and y = sin(theta).
In the same triangle, tan(theta)=x/y, so substituting we get tan(theta) = sin(theta)/cos(theta), the tangent identity.
Another key trigonometric identity sin2(theta) + cos2(theta) = 1 comes from using the unit circle and the Pythagorean Theorem.
Trigonometric Identities: How to Derive / Remember Them - Part 1 of 3.
Trigonometric Identities: How to Derive / Remember Them - Part 2 of 3.
Trigonometric Identities: How to Derive / Remember Them - Part 3 of 3.
Fundamental Trigonometric Identities
The reciprocal identities, quotient identities and the Pythagorean identities.
Trigonometric Identities
Deriving Trigonometric Identities from 3 Known Identities
Try the free Mathway calculator and
problem solver below to practice various math topics. Try the given examples, or type in your own
problem and check your answer with the step-by-step explanations.
We welcome your feedback, comments and questions about this site or page. Please submit your feedback or enquiries via our Feedback page.