SOFITO_SOFT
Sorry, English is my only language and I don't understand your meaning in the last post..
Just a note on the result you are expecting.
I asked how the data was being collected and you chose not to answer, so ...
I believe that the angle you are returning is useless without having a point of reference ... how do you know if the joint is viewed from the inside or the outside, whether the result is actually truly 15 degrees acute or 105 degrees convex or 165 degrees concave.
That is, I believe you need to provide a reference point to indicate which side of the planes the angle is measures.
In fact, planes are considered boundless, so you may also need to express (or consider) if you are assuming that the planes terminate at their intersection joint.
If the plane selection process is manual and the user has a chance to use his judgement the chance of misinterpretation is minimised somewhat ;
but if you are feeding your program large quantities of plane definition points and basing future decisions on possibly incorrect results I can see a lot of pain in your future.
Regards
Kerry
Picture added :