reserve X for non empty set,
        x for Element of X,
        S for SigmaField of X,
        M for sigma_Measure of S,
        f,g,f1,g1 for PartFunc of X,REAL,
        l,m,n,n1,n2 for Nat,
        a,b,c for Real;

theorem Th1:
for m,n be positive Real st 1/m + 1/n = 1 holds m > 1
proof
   let m,n be positive Real;
   assume 1/m +1/n =1; then
A1:1/n = 1-1/m;
   assume m <=1; then
   1<= 1/m by XREAL_1:181;
   hence contradiction by A1,XREAL_1:47;
end;
