Condition for Straight Lines in Plane to be Perpendicular/Slope Form/Proof 2
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Theorem
Let $L_1$ and $L_2$ be straight lines in the Cartesian plane.
Let the slope of $L_1$ and $L_2$ be $\mu_1$ and $\mu_2$ respectively.
Then $L_1$ is perpendicular to $L_2$ if and only if:
- $\mu_1 = -\dfrac 1 {\mu_2}$
Proof
This is a special case of Slope of Orthogonal Curves.
$\blacksquare$