theorem :: INTEGR13:45

for A being non empty closed_interval Subset of REAL
for f, f1 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
f1 . x = 1 ) & f = arccot / (f1 + (#Z 2)) & Z c= ].(- 1),1.[ & Z c= dom ((#Z 2) * arccot) & Z = dom f & f | A is continuous holds
integral (f,A) = ((- ((1 / 2) (#) ((#Z 2) * arccot))) . (upper_bound A)) - ((- ((1 / 2) (#) ((#Z 2) * arccot))) . (lower_bound A))