
### Instruction: help me answer this question Grouping the terms, = (cos2 x + sin2 x) + (cos2 y + sin2 y) – 2 (cos x cos y + sin x sin y), think step by step
### Assistant: N/A , The answer is By using the formula cos (A – B) = cos A cos B + sin A sin B, this can be simplified to: 1 + 1 – 2 [cos (x – y)]
