Pre-Calculus 12 Notes

By: Gen L.

Lesson 3: Sum & Difference Identities

Sum & Difference

Is ?

• No!
• Remember, cosine is a function, but without an angle, it means nothing.
• Therefore, we cannot distribute the function through.

The Identities

9. 
   Check using

What can we do with these?

Simplification

Write as a single trig function:

Write as a single trig function:

Exact Values

If the angle is a sum or difference of 2 special angles, we can find the exact value.

Proofs

Let's try proving more identities.

Simplification

Simplify

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