for A, B, C being Point of (TOP-REAL 2) st A,B,C is_a_triangle holds
( not angle (A,B,C) is zero & not angle (B,C,A) is zero & not angle (C,A,B) is zero & not angle (A,C,B) is zero & not angle (C,B,A) is zero & not angle (B,A,C) is zero )