Step 1:

The trigonometric expression is $\"\"$ .

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

Since $\"\"$ is positive, $\"\"$ is a first - quadrant angle.

Step 2:

Draw a right triangle with positive angle $\"\"$ .

$\"\"$

An algebraic expression of $\"\"$ is $\"\"$ .

Solution :

An algebraic expression of $\"\"$ is $\"\"$ .