let T be non empty RelStr ; :: thesis: for A, B being Subset of T
for n being Element of NAT holds (Fcl (A,n)) \/ (Fcl (B,n)) = (Fint (((A \/ B) `),n)) `
let A, B be Subset of T; :: thesis: for n being Element of NAT holds (Fcl (A,n)) \/ (Fcl (B,n)) = (Fint (((A \/ B) `),n)) `
let n be Element of NAT ; :: thesis: (Fcl (A,n)) \/ (Fcl (B,n)) = (Fint (((A \/ B) `),n)) `
(Fcl (A,n)) \/ (Fcl (B,n)) = Fcl ((A \/ B),n) by Th17
.= (Fint (((A \/ B) `),n)) ` by Th27 ;
hence (Fcl (A,n)) \/ (Fcl (B,n)) = (Fint (((A \/ B) `),n)) ` ; :: thesis: verum