Step 1 :

Find the trigonometric function $\"\"$ .

From the diagram : opposite side is $\"\"$ and adjacent side is $\"\"$ .

Pythagorean theorem : $\"\"$ .

$\"\"$

The trigonometric function : $\"\"$ .

To find $\"\"$ , use half-angle formula.

Half-angle formula : $\"\"$

$\"\"$

The exact value of $\"\"$ is $\"\"$ .

Solution :

The exact value of $\"\"$ is $\"\"$ .