\

The expression is $\"\"$ .

\

Simplify $\"\"$ .

\

Addition formula: $\"\"$ .

\

$\"\"$

\

Trigonometric identity: $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

\

$\"\"$

\

\

Fundamental trigonometric identity: $\"\"$ .

\

$\"\"$

\

\

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