theorem :: INTEGR13:13

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 & f1 = #Z 2 & f = (- ((sin / cos) / f1)) + (((id Z) ^) / (cos ^2)) & Z c= dom (((id Z) ^) (#) tan) & Z = dom f & f | A is continuous holds
integral (f,A) = ((((id Z) ^) (#) tan) . (upper_bound A)) - ((((id Z) ^) (#) tan) . (lower_bound A))