reserve X,Y for set, x,y,z for object, i,j,n for natural number;
reserve
  n for non empty Nat,
  S for non empty non void n PC-correct PCLangSignature,
  L for language MSAlgebra over S,
  F for PC-theory of L,
  A,B,C,D for Formula of L;

theorem Th44:
  B in F implies A\impB in F
proof
  B\imp(A\impB) in F by Def38;
  hence thesis by Def38;
end;
