IF I have two 3d planes such as Oab and Oa'b'. If these two planes intersect a horizontal plane and the intersection of each plane makes AB and A'B' lines. then,
Does the angle between AB, A'B' i.e. APA' is equal to the angle between XY projected normal vectors (i.e. XY projected n1 and n2 or angle between steepest gradient) of the planes?
Does this scenario is always true, even if we intersect these two planes with third plane which is not horizotal (i.e. instead of XY , if there is oblique plane)?
Please, answer my both questions.