Question

I need help with my practice test homework with question 1

Answer 1

By definition, we have the following identities

`\begin{gathered} \cos (\alpha+\beta)=\cos \alpha\cos \beta-\sin \alpha\sin \beta \\ \cos (\alpha-\beta)=\cos \alpha\cos \beta+\sin \alpha\sin \beta \end{gathered}`

Therefore, the only wrong option is option B.