let AS be AffinSpace; :: thesis: for A being being_line Subset of AS holds A // A
let A be being_line Subset of AS; :: thesis: A // A
consider a, b being Element of AS such that
A1: a <> b and
A2: A = Line (a,b) by Def3;
a,b // a,b by Th1;
hence A // A by A1, A2, Th36; :: thesis: verum