If I have not misunderstood, in [111] tetrahedrite ...

Description: If I have not misunderstood, in [111] tetrahedrite penetration twin (second version, as the last Smorf image) the angles between edges (here marked in yellow) should be 20º. Doesn't matter if there is some translational movement but the angles must stay constant. Is hard to see in photo but to me they seem bigger than 20º. However, the angle of the negative edge seems to be near 120º as it must be...