Ltac CopR :=
 let tpoint := constr:(Tpoint) in
 let col := constr:(Col) in
 let cop := constr:(Coplanar) in
   assert_ncols; Cop_refl tpoint col cop.

Lemma image_in_col0 : forall A B P P' Y : Tpoint, ReflectL_at Y P P' A B -> Col P P' Y.