$\"\"$

Vectors $\"\"$ and $\"\"$ are parallel.

Let the vectors $\"\"$ and $\"\"$ .

Directed angle of $\"\"$ : $\"\"$

$\"\"$

Directed angle of $\"\"$ : $\"\"$

$\"\"$

If the vectors are parallel then the directed angles must be equal.

$\"\"$

If $\"\"$ then $\"\"$ for any real number $\"\"$ .

Thus, $\"\"$ .

Vector equating relating $\"\"$ and $\"\"$ is $\"\"$ .

$\"\"$

Vector equating relating $\"\"$ and $\"\"$ is $\"\"$ .