$\"\"$

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The trigonometric equation is $\"\"$ .

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$\"\"$

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$\"\"$ and $\"\"$ .

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$\"\"$ and $\"\"$ .

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Since the range of $\"\"$ is $\"\"$ , the equation $\"\"$ has no solution.

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$\"\"$

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Solve the equation $\"\"$ .

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$\"\"$

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$\"\"$

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The general solution of $\"\"$ is $\"\"$ .

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Where $\"\"$ .

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$ and $\"\"$

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$\"\"$ and $\"\"$

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Solutions for $\"\"$ in the interval $\"\"$ are $\"\"$ and $\"\"$ .

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$\"\"$

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Solutions for $\"\"$ in the interval $\"\"$ are $\"\"$ and $\"\"$ .