RailwayRouteOptimization/scripts/Draw/Line/LineOrthogonalTangent/doc/LineOrthogonalTangent_proc_ru.html

<ol>
  <li>Click the line entity to which the new line should be orthogonal.</li>
  <li>Click the arc, circle or ellipse entity to which the line should be a
  tangent. There are two possible solutions. When moving the mouse around, you
  can see a preview of the tangent that will be created.</li>
</ol>