compound angles

Question

The formula for cos(A + B) is

RankGuru · Accepted Answer

1. **Addition Theorem**: The cosine of a sum follows a 'like-with-like' pattern but flips the sign.
2. **Result**: $\cos(A + B) = \cos A \cos B - \sin A \sin B$.
3. **Rule**: Cosine keeps $c\cdot c$ and $s\cdot s$ together, but $+$ in the argument results in $-$ in the expansion.

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More compound angles Practice Questions

The formula for sin(A + B) is