TRIG IDENTITIES

What is an identity?

Identity: a statement of equality that is TRUE as long as neither side is undefined.

Except when x = -1

Basic Identities

Why?

Other identities based on P.T. identity:

Cofunctions

A

B

Cofunction Identities

Sin(40) = Sin(-40)=

Cos(40)= Cos(-40)=

Even-Odd Identities

We will be doing 5 things with identities…

Evaluating – finding a value (numerical answer)

Simplifying – condensing (answer is usually a single trig function)

Factoring – un-doing the box/FOIL

Solving – getting “x” by itself (up to 4 possible solutions)

Verifying/Proving: showing that the left side and right side are equivalent.

Ex 1. Evaluate

Find the value of sine & cosine if

Ex 1. Find a trig function

Ex 2. Simplify

Ex 3. Factor

Ex.4 Solve

You Try