theorem Th65:
  exp_R is_differentiable_on REAL & diff(exp_R,th)=exp_R.th
proof
A1: [#]REAL is open Subset of REAL & REAL c=dom exp_R by FUNCT_2:def 1;
 for r st r in REAL holds exp_R is_differentiable_in r by Th64;
  hence thesis by A1,Th64,FDIFF_1:9;
end;
