$\"\"$

Let $\"\"$ , where $\"\"$ .

$\"\"$ is the angle between the $\"\"$ and $\"\"$ .

Dot product formula: $\"\"$ .

$\"\"$ .

$\"\"$

$\"\"$ .

Consider $\"\"$ .

$\"\"$

$\"\"$ .

Substitute $\"\"$ and $\"\"$ in $\"\"$ .

Therefore $\"\"$ .

$\"\"$

$\"\"$ .