$\"\"$

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The trigonometric equation is $\"\"$ .

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$\"\"$ (Write original equation)

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$\"\"$ (Subtract $\"\"$ from each side)

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$\"\"$ (Apply half angle formula: $\"\"$ )

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$\"\"$ (Apply square each side)

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$\"\"$ (Apply formula: $\"\"$ )

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$\"\"$ (Subtract $\"\"$ from each side)

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$\"\"$ (Apply LCM rule: $\"\"$ )

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$\"\"$ (Simplify) $\"\"$ $\"\"$

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$\"\"$

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$\"\"$ (Write factors form)

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$\"\"$ (Set 1 equals to zero)

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$\"\"$ (Set 2 equals to zero) $\"\"$

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Let $\"\"$ , the function $\"\"$ has a period of $\"\"$ , first find all solutions in the interval $\"\"$ .

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The function $\"\"$ is negative in second and third quadrant; and the function $\"\"$ is positive in first and fourth quadrant.

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So the solutions are $\"\"$ ; and substitute in $\"\"$ .

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$\"\"$ (Substitute $\"\"$ )

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$\"\"$ (Substitute $\"\"$ ) $\"\"$

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The solutions are $\"\"$ .