$\"\"$

The trigonometric function is $\"\"$ .

Consider $\"\"$ .

The reciprocal identity of $\"italic$ .

$\"\"$

The difference formula for the cosine function: $\"italic$ . $\"\"$

Divide numerator and denominator by $\"begin$ .

$\"equal$ \ \

$\"equal$

Apply quotient property: $\"italic$ .

Apply reciprocal property: $\"italic$ .

$\"equal$

$\"\"$ .

$\"\"$

$\"\"$ .