reserve p,q,r,th,th1 for Real;
reserve n for Nat;

theorem Th35:
  cosh is_differentiable_on REAL & diff(cosh,p)=sinh.p
proof
A1: [#]REAL is open Subset of REAL & REAL c=dom cosh by FUNCT_2:def 1;
  for r st r in REAL holds cosh is_differentiable_in r by Th32;
  hence thesis by A1,Th32,FDIFF_1:9;
end;
