Now I have a coordination system 'T', above a level plan, and have a pitch and roll angle 'P' and 'R' to the level plan.

At the beginning, this coordination system 'T' don't know 'P' and 'R', but 'T' know 3 arbitrarily points on the level plan with coordinate of 'T'.

In theory, knowing 3 arbitrarily points was enough to form a plan, so, how to calculate 'P' and 'R' with the 3 points coordinate (xa,ya,za) ; (xb,yb,zb) and (xc,yc,zc)?

Thank you very much!