$\"\"$

\

The trigonometric function is $\"\"$ .

\

Consider $\"\"$ .

\

Apply even-odd identity : $\"\"$ .

\

$\"\"$ .

\

Using the scientific calculator : $\"\"$ .

\

Using the Graphing calculator : $\"\"$ .

\

Thus, the value of $\"\"$ .

\

$\"\"$

\

The value of $\"\"$ .