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2 sin^2 x - cos x -1=0
2 sin²x - cos x - 1 = 0
2(1 - cos²x) - cos x -1 = 0
2 - 2 cos²x - cos x - 1 = 0
- 2 cos²x - cos x + 1 = 0
2 cos²x + cos x - 1 = 0
D = 1 + 8 = 9
√D = 3
cosx₁ = (-1 - 3): 4 = -1
cosx₂ = (-1 + 3): 4 = 1/2
x₁= π + 2πn
x₂ = π/3 + 2πn
x₃ = -π/3 + 2πn
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Answers & Comments
2 sin²x - cos x - 1 = 0
2(1 - cos²x) - cos x -1 = 0
2 - 2 cos²x - cos x - 1 = 0
- 2 cos²x - cos x + 1 = 0
2 cos²x + cos x - 1 = 0
D = 1 + 8 = 9
√D = 3
cosx₁ = (-1 - 3): 4 = -1
cosx₂ = (-1 + 3): 4 = 1/2
x₁= π + 2πn
x₂ = π/3 + 2πn
x₃ = -π/3 + 2πn