let AS be AffinSpace; :: thesis: for a, b being Element of AS holds
( a in Line a,b & b in Line a,b )
let a, b be Element of AS; :: thesis: ( a in Line a,b & b in Line a,b )
A1: LIN a,b,b by Th16;
LIN a,b,a by Th16;
hence ( a in Line a,b & b in Line a,b ) by A1, Def2; :: thesis: verum