(3)

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Step 1:

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The trigonometric value is $\"\"$ .

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Rewrite value as $\"\"$ .

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$\"\"$

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Since $\"\"$ .

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Substitute the values of $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$

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Step 1:

\

The trigonometric value is $\"\"$ .

\

Rewrite value as $\"\"$ .

\

$\"\"$

\

Since $\"\"$ .

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Substitute the values of $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$

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Step 1:

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The trigonometric expression is $\"\"$ .

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Use the trigonometric identity $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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The range of $\"\"$ is $\"\"$ . \ \

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So $\"\"$ .

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$\"\"$ .

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The general solution of $\"\"$ is $\"\"$ ,where $\"\"$ is integer.

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Step 2:

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$\"\"$

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if $\"\"$ then $\"\"$ .

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if $\"\"$ then

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$\"\"$ .

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$\"\"$ is out of the interval.

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The solution of the trigonometric expression is $\"\"$ in the interval $\"\"$ .

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