$\"\"$

The trigonometric expression is $\"\"$ .

Consider $\"\"$ .

Let $\"\"$ .

Therefore, $\"\"$ .

The relationship between $\"\"$ and $\"\"$ can be represented by a right triangle.

$\"\"$

$\"\"$ .

Observe the figure,

$\"\"$

$\"\"$ .

Thus, $\"\"$ . $\"\"$

$\"\"$ .