let Z be open Subset of REAL; :: thesis: ( Z c= dom (arctan * exp_R) & ( for x being Real st x in Z holds
exp_R . x < 1 ) implies ( arctan * exp_R is_differentiable_on Z & ( for x being Real st x in Z holds
((arctan * exp_R) `| Z) . x = (exp_R . x) / (1 + ((exp_R . x) ^2)) ) ) )
assume that
A1: Z c= dom (arctan * exp_R) and
A2: for x being Real st x in Z holds
exp_R . x < 1 ; :: thesis: ( arctan * exp_R is_differentiable_on Z & ( for x being Real st x in Z holds
((arctan * exp_R) `| Z) . x = (exp_R . x) / (1 + ((exp_R . x) ^2)) ) )
A3: for x being Real st x in Z holds
arctan * exp_R is_differentiable_in x

proof

let x be Real; :: thesis: ( x in Z implies arctan * exp_R is_differentiable_in x )
A4: exp_R is_differentiable_in x by SIN_COS:65;
assume x in Z ; :: thesis: arctan * exp_R is_differentiable_in x
then A5: exp_R . x < 1 by A2;
(exp_R . x) + 0 > 0 + (- 1) by SIN_COS:54;
hence arctan * exp_R is_differentiable_in x by A5, A4, Th85; :: thesis: verum

end;

then A6: arctan * exp_R is_differentiable_on Z by A1, FDIFF_1:9;
for x being Real st x in Z holds
((arctan * exp_R) `| Z) . x = (exp_R . x) / (1 + ((exp_R . x) ^2))

proof

let x be Real; :: thesis: ( x in Z implies ((arctan * exp_R) `| Z) . x = (exp_R . x) / (1 + ((exp_R . x) ^2)) )
A7: (exp_R . x) + 0 > 0 + (- 1) by SIN_COS:54;
A8: exp_R is_differentiable_in x by SIN_COS:65;
assume A9: x in Z ; :: thesis: ((arctan * exp_R) `| Z) . x = (exp_R . x) / (1 + ((exp_R . x) ^2))
then A10: exp_R . x < 1 by A2;
((arctan * exp_R) `| Z) . x = diff ((arctan * exp_R),x) by A6, A9, FDIFF_1:def 7
.= (diff (exp_R,x)) / (1 + ((exp_R . x) ^2)) by A7, A10, A8, Th85
.= (exp_R . x) / (1 + ((exp_R . x) ^2)) by SIN_COS:65 ;
hence ((arctan * exp_R) `| Z) . x = (exp_R . x) / (1 + ((exp_R . x) ^2)) ; :: thesis: verum

end;

hence ( arctan * exp_R is_differentiable_on Z & ( for x being Real st x in Z holds
((arctan * exp_R) `| Z) . x = (exp_R . x) / (1 + ((exp_R . x) ^2)) ) ) by A1, A3, FDIFF_1:9; :: thesis: verum