A common question is to express cos3θ in terms of cosθ and sin3θ in terms of sinθ.

Here is how you do it using the addition and double angle identities.

## cos 3θ in terms of cos θ

Example:

## sin 3θ in terms of sin θ

Example:

A common question is to express cos3θ in terms of cosθ and sin3θ in terms of sinθ.

Here is how you do it using the addition and double angle identities.

Example:

Example: