RailwayRouteOptimization/scripts/Draw/Line/LineRelativeAngle/doc/LineRelativeAngle_desc_en.html

<p>Create lines with a relative angle to existing entities with this tool. The
existing entity can be a line or an arc / circle. Lines with a relative angle
of 0 degrees to an arc are tangents or parallels to tangents. Lines with a
relative angle of 90 degrees to an arc or line are orthogonal lines.</p>