\

The expression is $\"\"$ .

\

$\"\"$

\

Consider $\"\"$ .

\

$\"\"$

\

Sum formula of tangent function : $\"\"$ .

\

$\"\"$

\

$\"\"$

\

Thus, $\"\"$ .

\

\

Substitute the value of $\"\"$ in $\"\"$ .

\

$\"\"$

\

\

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