How create perpendicular with revit api

[AndrewButenko]

I have p0 as XYZ and p1 as XYZ .

I need to get a line that is perpendicular to the line p0-p1 and ends at point p0 and has a length = d

[aignatovich]

Hi!

This is basic geometry task

Look at https://forums.autodesk.com/t5/revit-api-forum/how-to-create-line-based-on-angle/td-p/7372827

in few words you need to calculate cross product between your line direction and the plane, where your line situated normal. This will be your perpendicular direction