let g, f be FinSequence of CQC-WFF ; :: thesis: rng (Sgm (seq ((len g),(len f)))) = seq ((len g),(len f))
seq ((len g),(len f)) c= Seg ((len g) + (len f)) by Th7;
hence rng (Sgm (seq ((len g),(len f)))) = seq ((len g),(len f)) by FINSEQ_1:def 13; :: thesis: verum