let X be set ; :: thesis: for x, y, z being Subset of X
for q being FinSequence of BOOLEAN holds len (MergeSequence <*x,y,z*>,q) = 3
let x, y, z be Subset of X; :: thesis: for q being FinSequence of BOOLEAN holds len (MergeSequence <*x,y,z*>,q) = 3
let q be FinSequence of BOOLEAN ; :: thesis: len (MergeSequence <*x,y,z*>,q) = 3
thus len (MergeSequence <*x,y,z*>,q) = len <*x,y,z*> by Def1
.= 3 by FINSEQ_1:62 ; :: thesis: verum