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Answer:
cos 2θ + cos θ = (2cos θ - 1)(cos θ + 1)
cos 2θ - cos θ = (2cos θ + 1)(cos θ - 1)
Step-by-step explanation:
cos 2θ + cos θ = 2cos²θ - 1 + cos θ
cos 2θ + cos θ = 2cos²θ + cos θ - 1
2cos θ - 1
cos θ + 1
cos 2θ + cos θ = (2cos θ - 1)(cos θ + 1)
cos 2θ - cos θ = 2cos²θ - 1 - cos θ
cos 2θ - cos θ = 2cos²θ - cos θ - 1
2cos θ + 1
cos θ - 1
cos 2θ - cos θ = (2cos θ + 1)(cos θ - 1)