The trigonometric equation is $\"\"$ .

$\"\"$

$\"\"$ .

Solve $\"\"$ .

The function $\"\"$ is negative in third and fourth quadrants.

$\"\"$ .

The solutions in the interval $\"\"$ are $\"\"$ .

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Solve $\"\"$ .

The function $\"\"$ is positive in first and second quadrants.

$\"\"$ .

The solutions in the interval $\"\"$ are $\"\"$ .

The solution set is $\"\"$ .