reserve a,b,c,d,x,y,w,z,x1,x2,x3,x4 , X for set;
reserve A for non empty set;
reserve i,j,k for Element of NAT;
reserve a,b,c,d for Real;
reserve y,r,s,x,t,w for Element of RAT+;
reserve z,z1,z2,z3,z4 for Quaternion;

theorem Th23:
  Rea <i> = 0 & Im1 <i> = 1 & Im2 <i> = 0 & Im3 <i> = 0
proof
  [*zz,jj*] = [*0,1,0,0*] by Lm3;
  hence thesis by Lm2,Th16;
end;
