theorem :: INTEGR11:71

for a being Real
for A being non empty closed_interval Subset of REAL
for Z being open Subset of REAL
for f, f1, f2, f3 being PartFunc of REAL,REAL st A c= Z & f = f1 - f2 & f2 = #Z 2 & ( for x being Real st x in Z holds
( f1 . x = a ^2 & f . x > 0 & f3 . x = x / a & f3 . x > - 1 & f3 . x < 1 & x <> 0 & a > 0 ) ) & dom (arccos * f3) = Z & Z = dom (((id Z) (#) (arccos * f3)) - ((#R (1 / 2)) * f)) & (arccos * f3) | A is continuous holds
integral ((arccos * f3),A) = ((((id Z) (#) (arccos * f3)) - ((#R (1 / 2)) * f)) . (upper_bound A)) - ((((id Z) (#) (arccos * f3)) - ((#R (1 / 2)) * f)) . (lower_bound A))