$\"\"$

The trigonometric equation is $\"\"$ .

Assume that $\"\"$ .

$\"\"$

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

$\"\"$ ; $\"\"$

Replace $\"\"$ with $\"\"$ .

$\"\"$ ; $\"\"$

Divide each side by 2.

$\"\"$ ; $\"\"$ . $\"\"$

Solutions for multiple angle equation is $\"\"$ and $\"\"$ .