$2$ planes and angle between them

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,

1. Does the angle between AB, A'B' i.e. APA' is equal to the angle between normal vectors (i.e. n1 and n2) of the planes?

2. 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)?

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It is not, in general, true that the angle between the normal vectors $n_1$ and $n_2$ of two planes is equal to the angle between the lines of intersection $AB$ and $A′B′$ of these two planes with a third plane.
@gnp: I said that the angle between $n_1$ and $n_2$ is NOT, in general, equal to the angle between the lines $AB$ and $A'B'$. The answer to Q1 is therefore 'no'. The answer to Q2 is also 'no'. –  Eckhard Mar 28 '13 at 10:48