$\"\"$

The expression is $\"\"$ .

$\"\"$

Using the periodic trignometry property: $\"\"$ .

$\"\"$

Using the even-odd trignometry properties: $\"\"$

$\"\"$

$\"\"$ .

$\"\"$ $\"\"$

$\"\"$

Apply the inverse trigonometric identity : $\"\"$ , where $\"\"$ .

$\"\"$ .

The exact value of $\"\"$ .

$\"\"$

$\"\"$ .