let a be Real; :: thesis: for A being non empty closed_interval Subset of REAL
for f, f2 being PartFunc of REAL,REAL
for Z being open Subset of REAL st A c= Z & ( for x being Real st x in Z holds
( f . x = a - x & f . x > 0 ) ) & dom (- (ln * f)) = Z & dom (- (ln * f)) = dom f2 & ( for x being Real st x in Z holds
f2 . x = 1 / (a - x) ) & f2 | A is continuous holds
integral (f2,A) = ((- (ln * f)) . (upper_bound A)) - ((- (ln * f)) . (lower_bound A))
let A be non empty closed_interval Subset of REAL; :: thesis: for f, f2 being PartFunc of REAL,REAL
for Z being open Subset of REAL st A c= Z & ( for x being Real st x in Z holds
( f . x = a - x & f . x > 0 ) ) & dom (- (ln * f)) = Z & dom (- (ln * f)) = dom f2 & ( for x being Real st x in Z holds
f2 . x = 1 / (a - x) ) & f2 | A is continuous holds
integral (f2,A) = ((- (ln * f)) . (upper_bound A)) - ((- (ln * f)) . (lower_bound A))
let f, f2 be PartFunc of REAL,REAL; :: thesis: for Z being open Subset of REAL st A c= Z & ( for x being Real st x in Z holds
( f . x = a - x & f . x > 0 ) ) & dom (- (ln * f)) = Z & dom (- (ln * f)) = dom f2 & ( for x being Real st x in Z holds
f2 . x = 1 / (a - x) ) & f2 | A is continuous holds
integral (f2,A) = ((- (ln * f)) . (upper_bound A)) - ((- (ln * f)) . (lower_bound A))
let Z be open Subset of REAL; :: thesis: ( A c= Z & ( for x being Real st x in Z holds
( f . x = a - x & f . x > 0 ) ) & dom (- (ln * f)) = Z & dom (- (ln * f)) = dom f2 & ( for x being Real st x in Z holds
f2 . x = 1 / (a - x) ) & f2 | A is continuous implies integral (f2,A) = ((- (ln * f)) . (upper_bound A)) - ((- (ln * f)) . (lower_bound A)) )
assume that
A1: A c= Z and
A2: for x being Real st x in Z holds
( f . x = a - x & f . x > 0 ) and
A3: dom (- (ln * f)) = Z and
A4: dom (- (ln * f)) = dom f2 and
A5: for x being Real st x in Z holds
f2 . x = 1 / (a - x) and
A6: f2 | A is continuous ; :: thesis: integral (f2,A) = ((- (ln * f)) . (upper_bound A)) - ((- (ln * f)) . (lower_bound A))
A7: f2 is_integrable_on A by A1, A3, A4, A6, INTEGRA5:11;
A8: - (ln * f) is_differentiable_on Z by A2, A3, FDIFF_4:3;
A9: for x being Element of REAL st x in dom ((- (ln * f)) `| Z) holds
((- (ln * f)) `| Z) . x = f2 . x

proof

let x be Element of REAL ; :: thesis: ( x in dom ((- (ln * f)) `| Z) implies ((- (ln * f)) `| Z) . x = f2 . x )
assume x in dom ((- (ln * f)) `| Z) ; :: thesis: ((- (ln * f)) `| Z) . x = f2 . x
then A10: x in Z by A8, FDIFF_1:def 7;
then ((- (ln * f)) `| Z) . x = 1 / (a - x) by A2, A3, FDIFF_4:3
.= f2 . x by A5, A10 ;
hence ((- (ln * f)) `| Z) . x = f2 . x ; :: thesis: verum

end;

dom ((- (ln * f)) `| Z) = dom f2 by A3, A4, A8, FDIFF_1:def 7;
then (- (ln * f)) `| Z = f2 by A9, PARTFUN1:5;
hence integral (f2,A) = ((- (ln * f)) . (upper_bound A)) - ((- (ln * f)) . (lower_bound A)) by A1, A3, A4, A6, A7, A8, INTEGRA5:10, INTEGRA5:13; :: thesis: verum