$\"\"$

The trigonometric function is $\"\"$ .

Consider $\"\"$

The sum formula for the sine function: $\"\"$ .

The difference formula for the sine function: $\"\"$ .

$\"\"$

Trignometric identity : $\"\"$ , then $\"\"$ .

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

$\"\"$

$\"\"$ .

$\"\"$

$\"\"$ .