let V be RealLinearSpace; :: thesis: for w, y being VECTOR of
for a, b being Element of holds a # b = b # a
let w, y be VECTOR of ; :: thesis: for a, b being Element of holds a # b = b # a
let a, b be Element of ; :: thesis: a # b = b # a
reconsider u = a, v = b as VECTOR of ;
thus a # b = u # v by Def8
.= b # a by Def8 ; :: thesis: verum