let a be Real; :: thesis: for Z being open Subset of REAL
for f, f1 being PartFunc of REAL ,REAL st Z c= dom (((2 * a) (#) f) - (id Z)) & f = ln * f1 & ( for x being Real st x in Z holds
( f1 . x = a + x & f1 . x > 0 ) ) holds
( ((2 * a) (#) f) - (id Z) is_differentiable_on Z & ( for x being Real st x in Z holds
((((2 * a) (#) f) - (id Z)) `| Z) . x = (a - x) / (a + x) ) )
let Z be open Subset of REAL ; :: thesis: for f, f1 being PartFunc of REAL ,REAL st Z c= dom (((2 * a) (#) f) - (id Z)) & f = ln * f1 & ( for x being Real st x in Z holds
( f1 . x = a + x & f1 . x > 0 ) ) holds
( ((2 * a) (#) f) - (id Z) is_differentiable_on Z & ( for x being Real st x in Z holds
((((2 * a) (#) f) - (id Z)) `| Z) . x = (a - x) / (a + x) ) )
let f, f1 be PartFunc of REAL ,REAL ; :: thesis: ( Z c= dom (((2 * a) (#) f) - (id Z)) & f = ln * f1 & ( for x being Real st x in Z holds
( f1 . x = a + x & f1 . x > 0 ) ) implies ( ((2 * a) (#) f) - (id Z) is_differentiable_on Z & ( for x being Real st x in Z holds
((((2 * a) (#) f) - (id Z)) `| Z) . x = (a - x) / (a + x) ) ) )
assume A1: ( Z c= dom (((2 * a) (#) f) - (id Z)) & f = ln * f1 & ( for x being Real st x in Z holds
( f1 . x = a + x & f1 . x > 0 ) ) ) ; :: thesis: ( ((2 * a) (#) f) - (id Z) is_differentiable_on Z & ( for x being Real st x in Z holds
((((2 * a) (#) f) - (id Z)) `| Z) . x = (a - x) / (a + x) ) )
then Z c= (dom ((2 * a) (#) f)) /\ (dom (id Z)) by VALUED_1:12;
then A2: ( Z c= dom (id Z) & Z c= dom ((2 * a) (#) f) ) by XBOOLE_1:18;
then A3: Z c= dom (ln * f1) by A1, VALUED_1:def 5;
A4: for x being Real st x in Z holds
(id Z) . x = (1 * x) + 0 by FUNCT_1:35;
then A5: ( id Z is_differentiable_on Z & ( for x being Real st x in Z holds
((id Z) `| Z) . x = 1 ) ) by A2, FDIFF_1:31;
A6: ( f is_differentiable_on Z & ( for x being Real st x in Z holds
(f `| Z) . x = 1 / (a + x) ) ) by A1, A3, Th1;
then A7: ( (2 * a) (#) f is_differentiable_on Z & ( for x being Real st x in Z holds
(((2 * a) (#) f) `| Z) . x = (2 * a) * (diff f,x) ) ) by A2, FDIFF_1:28;
A8: for x being Real st x in Z holds
(((2 * a) (#) f) `| Z) . x = (2 * a) / (a + x)

proof

let x be Real; :: thesis: ( x in Z implies (((2 * a) (#) f) `| Z) . x = (2 * a) / (a + x) )
assume A9: x in Z ; :: thesis: (((2 * a) (#) f) `| Z) . x = (2 * a) / (a + x)
hence (((2 * a) (#) f) `| Z) . x = (2 * a) * (diff f,x) by A2, A6, FDIFF_1:28
.= (2 * a) * ((f `| Z) . x) by A6, A9, FDIFF_1:def 8
.= (2 * a) * (1 / (a + x)) by A1, A3, A9, Th1
.= (2 * a) / (a + x) by XCMPLX_1:100 ;
:: thesis: verum

end;

for x being Real st x in Z holds
((((2 * a) (#) f) - (id Z)) `| Z) . x = (a - x) / (a + x)

proof

let x be Real; :: thesis: ( x in Z implies ((((2 * a) (#) f) - (id Z)) `| Z) . x = (a - x) / (a + x) )
assume A10: x in Z ; :: thesis: ((((2 * a) (#) f) - (id Z)) `| Z) . x = (a - x) / (a + x)
then A11: ( f1 . x = a + x & f1 . x > 0 ) by A1;
((((2 * a) (#) f) - (id Z)) `| Z) . x = (diff ((2 * a) (#) f),x) - (diff (id Z),x) by A1, A5, A7, A10, FDIFF_1:27
.= (diff ((2 * a) (#) f),x) - (((id Z) `| Z) . x) by A5, A10, FDIFF_1:def 8
.= ((((2 * a) (#) f) `| Z) . x) - (((id Z) `| Z) . x) by A7, A10, FDIFF_1:def 8
.= ((((2 * a) (#) f) `| Z) . x) - 1 by A2, A4, A10, FDIFF_1:31
.= ((2 * a) / (a + x)) - 1 by A8, A10
.= ((2 * a) - (1 * (a + x))) / (a + x) by A11, XCMPLX_1:127
.= (a - x) / (a + x) ;
hence ((((2 * a) (#) f) - (id Z)) `| Z) . x = (a - x) / (a + x) ; :: thesis: verum

end;

hence ( ((2 * a) (#) f) - (id Z) is_differentiable_on Z & ( for x being Real st x in Z holds
((((2 * a) (#) f) - (id Z)) `| Z) . x = (a - x) / (a + x) ) ) by A1, A5, A7, FDIFF_1:27; :: thesis: verum