Let $C$ be a cline, $z$ and $z^{*}$ be two distinct symmetric points w.r.t. $C$.
Then
- Any cline $C'$ that is orthogonal to $C$ and passing through $z$, must also pass through $z^{*}$.
And its converse
- Any cline passing through $z$ and $z^{*}$, is orthogonal to $C$.
I have an idea, since all clines are congruent in hyperbolic geometry, and all Mobius transformations preserve angles and pairs of symmetric points. We can simply consider the case with $C$ being a straight line, but I am not sure how to continue...