When two shapes have been translated the angles stay congruent and in symmetry the angles stay the same. The sides only magnify to a larger measure in projection and scale change.
You can also check the rotational fit for both shapes.
If the line appears to be different line after rotation ie) facing east after rotation would be 90 degree rotation if it fits then the angle has not changed for 4 sided shape, for 3 sided this would be 60 degree for equilaterial or a different angle that matches one other angle for isosceles, you can count the vertices and see if rotation fits for the same points rotational points of change.
