$\"\"$

The identity is $\"\"$ .

To take the left hand side expression for prove that right hand side expression.

$\"\"$

(Apply quotient identities: $\"\"$ ) \ \

$\"\"$

$\"\"$ (Add: $\"\"$ ) \ \

$\"\"$ (Apply Pythagorean identity: $\"\"$ )

(Apply reciprocal identities: $\"\"$ ) \ \

$\"\"$ $\"\"$

$\"\"$ is not an identity.