let A be non empty closed_interval Subset of REAL; :: thesis: for Z being open Subset of REAL
for f1, f2 being PartFunc of REAL,REAL st A c= Z & Z c= ].(- 1),1.[ & f2 = #Z 2 & ( for x being Real st x in Z holds
f1 . x = 1 ) & dom arccot = Z & Z = dom (((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) holds
integral (arccot,A) = ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) . (upper_bound A)) - ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) . (lower_bound A))
let Z be open Subset of REAL; :: thesis: for f1, f2 being PartFunc of REAL,REAL st A c= Z & Z c= ].(- 1),1.[ & f2 = #Z 2 & ( for x being Real st x in Z holds
f1 . x = 1 ) & dom arccot = Z & Z = dom (((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) holds
integral (arccot,A) = ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) . (upper_bound A)) - ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) . (lower_bound A))
let f1, f2 be PartFunc of REAL,REAL; :: thesis: ( A c= Z & Z c= ].(- 1),1.[ & f2 = #Z 2 & ( for x being Real st x in Z holds
f1 . x = 1 ) & dom arccot = Z & Z = dom (((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) implies integral (arccot,A) = ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) . (upper_bound A)) - ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) . (lower_bound A)) )
assume that
A1: A c= Z and
A2: Z c= ].(- 1),1.[ and
A3: ( f2 = #Z 2 & ( for x being Real st x in Z holds
f1 . x = 1 ) ) and
A4: dom arccot = Z and
A5: Z = dom (((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) ; :: thesis: integral (arccot,A) = ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) . (upper_bound A)) - ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) . (lower_bound A))
( ].(- 1),1.[ c= [.(- 1),1.] & A c= ].(- 1),1.[ ) by A1, A2, XBOOLE_1:1, XXREAL_1:25;
then arccot | A is continuous by FCONT_1:16, SIN_COS9:54, XBOOLE_1:1;
then A6: ( arccot is_integrable_on A & arccot | A is bounded ) by A1, A4, INTEGRA5:10, INTEGRA5:11;
A7: ((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2))) is_differentiable_on Z by A2, A3, A5, SIN_COS9:104;
A8: for x being Element of REAL st x in dom ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) `| Z) holds
((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) `| Z) . x = arccot . x

proof

let x be Element of REAL ; :: thesis: ( x in dom ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) `| Z) implies ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) `| Z) . x = arccot . x )
assume x in dom ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) `| Z) ; :: thesis: ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) `| Z) . x = arccot . x
then x in Z by A7, FDIFF_1:def 7;
hence ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) `| Z) . x = arccot . x by A2, A3, A5, SIN_COS9:104; :: thesis: verum

end;

dom ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) `| Z) = dom arccot by A4, A7, FDIFF_1:def 7;
then (((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) `| Z = arccot by A8, PARTFUN1:5;
hence integral (arccot,A) = ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) . (upper_bound A)) - ((((id Z) (#) arccot) + ((1 / 2) (#) (ln * (f1 + f2)))) . (lower_bound A)) by A1, A2, A3, A5, A6, INTEGRA5:13, SIN_COS9:104; :: thesis: verum