$\"\"$

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The trigonometric equation is $\"\"$ .

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$\"\"$

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Double angle formula: $\"\"$ .

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$\"\"$

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$\"\"$

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The general form of equation is $\"\"$ .

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Compare the equation with general equation.

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$\"\"$

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Hence,

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$\"\"$

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Therefore ,the function has no real solution.

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$\"\"$

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The function has no real solution.