let D be set ; :: thesis: for p, q, r being Element of D * holds FlattenSeq <*p,q,r*> = (p ^ q) ^ r
let p, q, r be Element of D * ; :: thesis: FlattenSeq <*p,q,r*> = (p ^ q) ^ r
consider g being BinOp of (D * ) such that
A1: for d1, d2 being Element of D * holds g . d1,d2 = d1 ^ d2 and
A2: FlattenSeq <*p,q,r*> = g "**" <*p,q,r*> by Def14;
thus FlattenSeq <*p,q,r*> = g . (g . p,q),r by A2, FINSOP_1:15
.= (g . p,q) ^ r by A1
.= (p ^ q) ^ r by A1 ; :: thesis: verum