2. Objective: Given a trigonometric equation, prove that it is an identity.

3. Purpose of Identities

4. Steps in Proving Identities Pick the member you wish to work with and write it down. Usually it is easier to start with the more complicated member. Look for algebraic things to do: If there are two terms and you want only one: Add fractions Factor something out. Multiply by a clever form of 1. To multiply a numerator or denominator by its conjugate. To get a desired expression in a numerator or denominator. Do any obvious algebra such as: Distributing Squaring Multiplying polynomials Look for trigonometric things to do: Look for familiar trigonometric expressions. If there are squares of functions, think of the Pythagorean properties. Keep looking at the answer to make sure you are headed in the right direction.

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