I hope someone can explain this to me. In the definition of Euler angles, the body-fixed-azimuthal angel γ is measured from the nodal line that defines the intersection of the body-fixed-XY plane and the space fixed-xy plane to the body-fixed-Y axis. This is the green line in this image from google and I am using here the same labels as in the image. Now, if the body-fixed-XYZ axes are rotated in space, say, about the space-fixed-z axis, How should one define the new nodal line? In other words, how one should measure the body-fixed-azimuthal angel γ after the rotation?