$\"\"$

The expression is $\"\"$ .

$\"\"$ (Apply Pythagorean identity)

$\"\"$ (Substitute $\"\"$ )

$\"\"$ (Evaluate power: $\"\"$ ) \ \ $\"\"$

$\"\"$ (Subtract 1 from each side)

$\"\"$ (Simplify)

$\"\"$ (Subtract: $\"\"$ )

$\"\"$ (Take the square root of each side)

$\"\"$ (Simplify)

$\"\"$ is in the third quadrant, tan $\"\"$ is positive,

Therefore $\"\"$ . $\"\"$

The value of $\"\"$ .