reserve X for set;
reserve a,b,c,k,m,n for Nat;
reserve i,j for Integer;
reserve r for Real;
reserve p,p1,p2 for Prime;

theorem Th29:
  m * n = 26 implies m = 1 & n = 26
                  or m = 2 & n = 13
                  or m = 13 & n = 2
                  or m = 26 & n = 1
  proof
    assume
A1: m*n = 26;
    m divides m*n;
    then m = 1 or m = 2 or m = 13 or m = 26 by A1,Th14;
    hence thesis by A1;
  end;
