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;
