
### Instruction: help me answer this question Prove that (cos x – cos y)^2 + (sin x – sin y)^2 = 2 - 2cos(x – y), think step by step
### Assistant: This involves the use of trigonometric formulas and simplification. , The answer is LHS = (cos^2 x + cos^2 y - 2cos x cos y) + (sin^2 x + sin^2 y - 2sin x sin y) = 2 - 2cos(x – y) = RHS
