# Trigonometric Identities

Related Topics:
More Lessons for Algebra II

Math Worksheets

Videos, worksheets, solutions, and activities to help Algebra 2 students learn about trigonometric identities.

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

Rotate to landscape screen format on a mobile phone or small tablet to use the Mathway widget which allows your to practice solving Algebra, Trigonometry, Calculus and other math topics.

You can use the Mathway widget below to practice Trigonometry or other math topics. Try the given examples, or type in your own problem. Then click "Answer" to check your answer.