reserve p1,p2,p3,p4,p5,p6,p,pc for Point of TOP-REAL 2;
reserve a,b,c,r,s for Real;
reserve c1,c2,c3 for Element of COMPLEX;

theorem
  not angle(p1,p2,p3) = 2*angle(p4,p5,p6)-6*PI by Lm6;
