$\"\"$

\

The trigonometric identity is $\"\"$ .

\

Find the value of $\"\"$ .

\

Rewrite the expression.

\

$\"\"$ .

\

Half-angle formula: $\"\"$ .

\

$\"\"$

\

Substitute $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

Therefore, $\"\"$ .

\

$\"\"$

\

Find the value of $\"\"$ .

\

Rewrite the expression.

\

$\"\"$

\

Hope half-angle formula: $\"\"$ .

\

$\"\"$

\

Substitute $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

Therefore, $\"\"$ .

\

$\"\"$

\

$\"\"$ and $\"\"$ .