theorem Th2: :: PDLAX:2

for a, b, c, d being Real
for f being PartFunc of REAL,REAL st a <= b & c <= d & [.a,b.] c= dom f & c in [.a,b.] & d in [.a,b.] & f | ['a,b'] is continuous & ( for t being Real st t in [.c,d.] holds
0 <= f . t ) holds
0 <= integral (f,c,d)