$\"\"$

The trigonometric expression is $\"\"$ .

Consider $\"\"$ , then $\"\"$

Definition of inverse trigonometric function : $\"\"$ .

If $\"\"$ , then $\"\"$ .

$\"\"$ .

$\"\"$

From Pythagorean theorem,

The square of the hypotenuse is equal to sum the squares of the other two sides.

$\"\"$

$\"\"$ .

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

$\"\"$ .

$\"\"$

$\"\"$ .