The trigonometric equation is $\"\"$ .

$\"\"$

The function $\"\"$ has a period of $\"\"$ , first find all solutions in the interval $\"\"$ .

General solution $\"\"$ :

If $\"\"$ , then $\"\"$ , where $\"\"$ is an integer.

$\"\"$

Solution for the interval of $\"\"$ .

The solution is $\"\"$ .