I am struggling to dynamically drive the angle projected on the view plane between non intersecting edges of two flexible components, from the dynamically driven angle between two other components in the mechanism.

The driven angle changes as a consequence of something else.  It is not under my control.  I want to measure it and drive the other angle the same magnitude in opposite rotation.

It is not clear how I can dimension an angle in an assembly.  If I could get a dimension I would have a name to insert in an equation for the other dimension.