# Using and Proving Trigonometric Identities

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Examples, videos, worksheets, solutions, and activities to help Algebra 2 and Grade 11 students learn how to use and prove trigonometric identities.

Using Trigonometric Identities
When simplifying problems that have reciprocal trig functions, start by substituting in the identities for each. If possible, write tangent in terms of sine and cosine. Use algebra to eliminate any complex fractions, factor, or cancel common terms. When using trigonometric identities, make one side of the equation look like the other or work on both sides of the equation to arrive at an identity (like 1=1).

How to simplify a trigonometric expression by converting to sines and cosines and using algebra.
Prove Trigonometric Identities Part 1
This lesson shows four examples (3 in part 1) regarding how to prove trigonometric identities.

Prove Trigonometric Identities Part 2
This lesson shows four examples (1 in part 2) regarding how to prove trigonometric identities.
Proving Trigonometric Identities
We can use the fundamental identities to prove other identities.

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