let a, b be Point of TarskiEuclid2Space; ( between a,a,b & between a,b,b )
Tn2TR a in LSeg ((Tn2TR a),(Tn2TR b))
by RLTOPSP1:68;
hence
between a,a,b
by ThConv6; between a,b,b
Tn2TR b in LSeg ((Tn2TR a),(Tn2TR b))
by RLTOPSP1:68;
hence
between a,b,b
by ThConv6; verum