theorem Th27: :: INTEGRA6:27

for a, b, c, d, e being Real
for f being PartFunc of REAL,REAL st a <= b & ( for x being Real st x in ['a,b'] holds
f . x = e ) & ['a,b'] c= dom f & c in ['a,b'] & d in ['a,b'] holds
integral (f,c,d) = e * (d - c)