### Home > PC > Chapter 6 > Lesson 6.2.2 > Problem 6-87

6-87.

Use the angle difference formula for cosine to simplify cos(*π* − *θ*). Write your answer as an identity and check it for *θ* = . Homework Help ✎

cos(*π* − *θ*) = cos*π* cos*θ* + sin*π* sin*θ*

= −1cos*θ* + 0 · sin*θ*

cos(*π* − *θ*) = −cos*θ*