Advances in the geometrical study of rotation-invariant t-norms

T-norm properties for left-continuous, increasing [0, 1](2)-> [0, 1.] functions can be fully described in terms of contour lines. For a left-continuous t-norm T, the rotation-invariance property comes down to the continuity of its contour line C-o. However, contour lines are inadequate to investigate the geometrical structure of these rotation-invariant t-norms. Enforced with the companion and zooms it is possible to totally reconstruct T by means of its contour line CO and its beta-zoom, with beta the unique fixpoint of C-o