$\"\"$

The trigonometric equation is $\"\"$ .

Add $\"\"$ to each side.

$\"\"$ .

$\"\"$

Subtract $\"1$ from each side.

$\"\"$ .

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

$\"\"$ .

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

$\"\"$

The solution set is $\"\"$ .