$\"\"$

The function is $\"\"$ .

Draw a coordinate plane.

Graph the function $\"\"$ .

Graph :

$\"\"$

Observe the above graph :

The graph appears to be equivalent to $\"\"$ .

$\"\"$

Check algebraically :

Consider $\"\"$ .

$\"\"$

Apply cosine sum identity : $\"\"$ .

Apply cosine difference identity : $\"\"$ .

$\"\"$

Pythagorean identity : $\"\"$ .

$\"\"$ .

$\"\"$

The function $\"\"$ appears to be equivalent to $\"\"$ .