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I need help with my practice test homework with question 1

I need help with my practice test homework with question 1-example-1
User Scribble
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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.

User SlavaGu
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