Angel between wall to X axis


im looking for a way to know the rotation of an element along X axis.
the challenge is how to know if the angel I got is a or180-a

Obtain the vector that captures the orientation of the element and then find it’s angle with the X-Axis using either Vector.AngleWithVector or Vector.AngleAboutAxis
A little work after obtaining the angle with the latter should give you the desired result.
If you still have trouble (or even if you succeed) please get back here with screenshots of your graph.

hope i more clear now,
how do i know if ill get a1/a2?

I will expand more information about my qestion.
I working on a graph that will help me to place formwork over concrete walls.
I created a generic model family (attach) that I can control the angle.
Now, I need to rotate the formwork by angle, but I can’t figure out the role angle between the X-axis.

run the graph and pick an Edge between 2 walls

Outside Formwork.rfa (340 KB)
form.dyn (73.6 KB)