theorem
  <*a,b,c*> = <*d,e,f*> implies a = d & b = e & c = f
proof
  assume
A1: <*a,b,c*> = <*d,e,f*>;
  thus a = <*a,b,c*>.1
    .= d by A1,Th45;
  thus b = <*a,b,c*>.2
    .= e by A1,Th45;
  thus c = <*a,b,c*>.3
    .= f by A1,Th45;
end;
