# Precalculus : Sum and Difference Identities For Cosine

## Example Questions

### Example Question #5 : Sum And Difference Identities

Use the sum or difference identity to find the exact value:

Explanation:

Using the identity, we can break up the 255 into and then solve:

### Example Question #1 : Sum And Difference Identities

Is the following equation an identity?

No it is not an identity.

It cannot be determined from the given information.

Yes it is an identity.

No it is not an identity.

Explanation:

and due to this inequality, this is not an identity

### Example Question #7 : Sum And Difference Identities

Use the sum or difference identity to find the exact value:

Explanation:

Using the identity, we can break up the  into  and then solve:  and so the correct answer is .

### Example Question #1 : Sum And Difference Identities

Is the following equation an identity?

The answer cannot be determined from the information provided.

Yes it is an identity

No it is not an identity

No it is not an identity

Explanation:

Due to this inequality, this is not an identity.

### Example Question #9 : Sum And Difference Identities

Use the sum or difference identity to find the exact value of .