theorem :: FDIFF_7:42

for Z being open Subset of REAL st Z c= dom ((sin + cos) / exp_R) holds
( (sin + cos) / exp_R is_differentiable_on Z & ( for x being Real st x in Z holds
(((sin + cos) / exp_R) `| Z) . x = - ((2 * (sin . x)) / (exp_R . x)) ) )