reserve A for QC-alphabet;
reserve sq for FinSequence,
  x,y,z for bound_QC-variable of A,
  p,q,p1,p2,q1 for Element of QC-WFF(A);
reserve s,t for bound_QC-variable of A;
reserve F,G,H,H1 for Element of QC-WFF(A);

theorem Th29:
  the_left_disjunct_of(F 'or' G) = F & the_right_disjunct_of(F
  'or' G) = G & the_argument_of F 'or' G = 'not' F '&' 'not' G
proof
  thus the_left_disjunct_of(F 'or' G) = the_argument_of the_left_argument_of (
  'not' F '&' 'not' G) by Th1
    .= the_argument_of 'not' F by Th4
    .= F by Th1;
  thus the_right_disjunct_of(F 'or' G) = the_argument_of the_right_argument_of
  ('not' F '&' 'not' G) by Th1
    .= the_argument_of 'not' G by Th4
    .= G by Th1;
  thus thesis by Th1;
end;
