$\"\"$

\

The trigonometric identity is $\"\"$ .

\

Consider the left hand side : $\"fraction$ .

\

$\"equal$

\

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

\

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

\

$\"equal$

\

$\"equal$

\

Apply quotient identity : $\"italic$ .

\

$\"equal$

\

= Right hand side identity.

\

$\"\"$

\

$\"\"$