$\"\"$

\

Observe the figure, u represented by directed line segment from $\"\"$ to $\"\"$ , and v represented by directed line segment from $\"\"$ to $\"\"$ and both are same direction.

\

$\"\"$ (Write distance formula)

\

$\"\"$ (Substitute: $\"\"$ )

\

$\"\"$ (Simplify)

\

$\"\"$ (Write distance formula)

\

$\"\"$ (Substitute: $\"\"$ )

\

$\"\"$ (Simplify) $\"\"$

\

$\"\"$ (Write slope formula)

\

$\"\"$ (Substitute: $\"\"$ )

\

$\"\"$ (Simplify)

\

$\"\"$ (Write slope formula)

\

$\"\"$ (Substitute: $\"\"$ )

\

$\"\"$ (Simplify) $\"\"$

\

The magnitude of u and v is same ( $\"\"$ ), the slope of u and v is same

\

( $\"\"$ ) and its direction is same, so they are equal.