$\"\"$

The trigonometric function is $\"\"$ .

Consider $\"\"$

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

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

$\"\"$

$\"\"$ .

Trignometry identity: $\"\"$ .

Substitute $\"\"$ and $\"\"$ in the integral equation.

$\"\"$

$\"\"$ .

$\"\"$

$\"\"$ .