let X be non empty set ; :: thesis: for S being SigmaField of X
for M being sigma_Measure of S
for f being PartFunc of X,REAL
for A, B being Element of S st ex E being Element of S st
( E = dom f & f is_measurable_on E ) & f is nonnegative & A misses B holds
Integral M,(f | (A \/ B)) = (Integral M,(f | A)) + (Integral M,(f | B))

let S be SigmaField of X; :: thesis: for M being sigma_Measure of S
for f being PartFunc of X,REAL
for A, B being Element of S st ex E being Element of S st
( E = dom f & f is_measurable_on E ) & f is nonnegative & A misses B holds
Integral M,(f | (A \/ B)) = (Integral M,(f | A)) + (Integral M,(f | B))

let M be sigma_Measure of S; :: thesis: for f being PartFunc of X,REAL
for A, B being Element of S st ex E being Element of S st
( E = dom f & f is_measurable_on E ) & f is nonnegative & A misses B holds
Integral M,(f | (A \/ B)) = (Integral M,(f | A)) + (Integral M,(f | B))

let f be PartFunc of X,REAL ; :: thesis: for A, B being Element of S st ex E being Element of S st
( E = dom f & f is_measurable_on E ) & f is nonnegative & A misses B holds
Integral M,(f | (A \/ B)) = (Integral M,(f | A)) + (Integral M,(f | B))

let A, B be Element of S; :: thesis: ( ex E being Element of S st
( E = dom f & f is_measurable_on E ) & f is nonnegative & A misses B implies Integral M,(f | (A \/ B)) = (Integral M,(f | A)) + (Integral M,(f | B)) )

assume that
A1: ex E being Element of S st
( E = dom f & f is_measurable_on E ) and
A2: ( f is nonnegative & A misses B ) ; :: thesis: Integral M,(f | (A \/ B)) = (Integral M,(f | A)) + (Integral M,(f | B))
consider E being Element of S such that
A3: E = dom f and
A4: f is_measurable_on E by A1;
R_EAL f is_measurable_on E by A4, Def6;
hence Integral M,(f | (A \/ B)) = (Integral M,(f | A)) + (Integral M,(f | B)) by A2, A3, MESFUNC5:97; :: thesis: verum