reserve q,r,c,c1,c2,c3 for Quaternion;
reserve x1,x2,x3,x4,y1,y2,y3,y4 for Real;

theorem
  c*'*' = c
proof
A1: Rea (c*') = Rea c by QUATERNI:44;
A2: Im1 (c*') = -Im1 c by QUATERNI:44;
A3: Im2 (c*') = -Im2 c by QUATERNI:44;
  Im3 (c*') = -Im3 c by QUATERNI:44;
  then c*'*'
  = [*Rea c, -(-Im1 c), -(-Im2 c), -(-Im3 c) *] by A1,A2,A3,QUATERNI:43
    .= c by QUATERNI:24;
  hence thesis;
end;
