let X be non empty set ; ( dom (canon_image X,1) = X & ( for x being set st x in X holds
(canon_image X,1) . x = [x,1] ) )
dom (canon_image X,1) = free_magma X,1
by FUNCT_2:def 1;
hence A1:
dom (canon_image X,1) = X
by Def14; for x being set st x in X holds
(canon_image X,1) . x = [x,1]
thus
for x being set st x in X holds
(canon_image X,1) . x = [x,1]
by A1, Def20; verum