$\"\"$

The expression is $\"\"$ .

Consider $\"\"$ .

From trigonometric identities $\"\"$

Therefore $\"\"$

$\"\"$

Replace the values of $\"\"$ with $\"\"$ , therefore $\"\"$ .

Use the properties of inverse trigonometric function: $\"\"$

$\"\"$

The exact value of expression $\"\"$ .

$\"\"$

The exact value of expression $\"\"$ .