Definition:Conjugate Lines

Definition
Let $\CC$ be a circle.

Let $\PP$ and $\QQ$ be the straight lines in the plane of $\CC$.

Let $P$ and $Q$ be the poles of $\PP$ and $\QQ$ with respect to $\CC$ respectively.

Let $P$ and $Q$ be such that $P$ lies on $\QQ$ and $Q$ lies on $\PP$.

Then $\PP$ and $\QQ$ are known as conjugate lines with respect to $\CC$.

Also see

 * Reciprocal Property of Pole and Polar


 * Definition:Conjugate Points (Geometry)