$\"\"$

The expression is $\"\"$ .

$\"\"$ (Apply pythagorean identity)

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

$\"\"$ (Simplify) \ \

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

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

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

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

$\"\"$ (Simplify)

$\"\"$ is in the first quadrant, sin $\"\"$ is positive,

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

The value of $\"\"$ .