The trigonometric expression is $\"\"$ .

Let $\"\"$ , then $\"\"$

$\"\"$ .

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

$\"\"$

$\"\"$ .

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

$\"\"$

$\"\"$ .

The algebric expression is $\"\"$ .