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
  c1=euc2cpx(p1-p2) & c2=euc2cpx(p3-p2) implies angle(p1,p2,p3) = angle(
  c1,c2) by Lm7;
