1) 8sin^2(x)- 4cos(x)-3=0

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8sin²(x) - 4cos(x) - 3 = 0

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Note: sin²A + cos²A = 1 than sin²A = 1 - cos²A

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8(1 - cos²x) - 4cos(x) - 3 = 0

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Simplify

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8 - 8cos²x - 4cos(x) - 3 = 0

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- 8cos²x - 4cos(x) - 3 + 8 = 0

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- 8cos²x - 4cos(x) + 5 = 0

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Multiply each side by negative one.

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8cos²x + 4cos(x) - 5 = 0

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Let cos(x) = t

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Than

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8t² + 4t + 5 = 0

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But t = cos(x)

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There fore

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