The trigonometric equation is $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

Let, $\"\"$ , then $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$ .

\

Let, $\"\"$ ,

\

$\"\"$ .

\

$\"\"$ , is a quadratic, use quadratic equation to find roots of the related quadratic function.

\

The solution of the quadratic equation : $\"\"$ is $\"\"$ .

\

Compare the equation $\"\"$ with $\"\"$ .

\

$\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

Put $\"\"$ .

\

$\"\"$

\

$\"\"$

\

put $\"\"$ .

\

$\"\"$ .

\

$\"\"$

\

$\"\"$ .

\

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

\

\

\

\

\

\