$\"\"$

\

The statement is $\"\"$ .

\

Consider $\"\"$ .

\

Let $\"\"$

\

Apply derivative on each side with respect to $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$ .

\

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

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

Substitute $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

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

\

$\"\"$ .

\

= Right hand side.

\

$\"\"$ .

\

The statement is true.

\

$\"\"$

\

The statement is true.