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

theorem Th11:
  0q = [*0,0,0,0*]
proof
  thus 0q = [*In(0,REAL),In(0,REAL)*] by ARYTM_0:def 5
    .= [*0,0,0,0*] by QUATERNI:91;
end;
