$\"\"$

\

The Trigonometric expression is $\"\"$ .

\

Consider $\"\"$ .

\

$\"\"$ .

\

$\"\"$ .

\

$\"\"$ is negative in second and third quadrants.

\

Apply Pythagorean theorem: $\"\"$ .

\

Substitute $\"\"$ and $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$ .

\

Since $\"\"$ is positive in second quadrant, $\"\"$ .

\

$\"\"$ .

\

$\"\"$

\

$\"\"$ .

\

$\"\"$

\

Substitute $\"\"$ in $\"\"$ .

\

$\"\"$

\

Apply double angle formula: $\"\"$ .

\

Substitute $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$ .

\

$\"\"$ .

\

$\"\"$

\

$\"\"$ .