In order to view 2 and 3 use the same method to find the angle 1. But I have to do to find the coordinates XY plane rotation by E0 around Z axis: 120 degrees counterclockwise and clockwise .
To find the corner 2 and 3 use the same method to find the corner 1 but need to be rated for 0 E by turning around the barrel Z XY horizontal 120 degrees counter-clockwise and clockwise