intros.
induction(eq_dec_points A B).
subst B.
assert(A' = B').
eapply proj_uniqueness.
apply H0.
assumption.
subst B'.
apply between_trivial2.
induction(eq_dec_points B C).
subst C.
assert(B' = C').
eapply proj_uniqueness.
apply H1.
assumption.
subst C'.
apply between_trivial.
assert(A <> C).
intro.
subst C.
apply between_identity in H.
contradiction.
induction (eq_dec_points A' C').
subst C'.
assert(A' = B').
eapply proj_perp_id.
4: apply H1.
3: apply H0.
3: apply H2.
assumption.
apply bet_col.
assumption.
subst B'.
apply l7_3_2.
assert(P <> Q).
eapply proj_diff.
apply H0.
assert(Col A' P Q).
eapply proj_col.
apply H0.
assert(Col B' P Q).
eapply proj_col.
apply H1.
assert(Col C' P Q).
eapply proj_col.
apply H2.
assert(Col A B C).
eapply bet_col.
assumption.
induction (eq_dec_points A A').
subst A'.
eapply (proj_preserves_bet1 A B C _ _ P Q); assumption.
assert(~Col A P Q).
intro.
apply proj_not_col in H0.
apply H0.
Col.
assumption.
induction (eq_dec_points B B').
subst B.
assert(C <> C').
intro.
subst C'.
apply H13.
assert(Col B' C P).
ColR.
assert(Col B' C Q).
ColR.
eapply (col3 B' C); Col.
apply col_permutation_1 in H9.
assert(~Col C P Q).
intro.
apply proj_not_col in H2.
apply H2.
Col.
assumption.
assert(HH:= proj_inv_exists P Q B' H7 H9).
ex_and HH B.
assert(HH:=proj_diff_not_col_inv B A B' A' P Q H16 H17 H0).
destruct HH.
assert(HH:=proj_diff_not_col_inv B C B' C' P Q H16 H17 H2).
destruct HH.
assert(HH:= proj_one_side B A B' A' P Q H16 H17 H0).
induction HH.
assert(B' = A').
apply H19.
Col.
subst B'.
apply between_trivial2.
assert(HH:= proj_one_side B C B' C' P Q H16 H17 H2).
induction HH.
assert(B' = C').
apply H21.
Col.
subst B'.
apply between_trivial.
(*********************************************)
assert(HH:=proj_diff_not_col_inv B A B' A' P Q H16 H17 H0).
destruct HH.
assert(HH:=proj_diff_not_col_inv B C B' C' P Q H16 H17 H2).
destruct HH.
assert(TS B B' A C).
unfold TS.
repeat split.
intro.
assert(B' = A').
apply H25.
Col.
subst B'.
assert(Col A' B C).
ColR.
assert(A' = C').
apply H27.
Col.
contradiction.
intro.
assert(B' = C').
apply H27.
Col.
subst B'.
assert(Col C' A C).
ColR.
assert(C' = A').
apply H25.
ColR.
subst C'.
tauto.
exists B'.
split; Col.
assert(TS B B' A' C).
eapply l9_8_2.
apply H28.
assumption.
assert(TS B B' C' A').
eapply l9_8_2.
apply l9_2.
apply H29.
assumption.
unfold TS in H30.
spliter.
ex_and H32 BB.
assert(BB= B').
eapply l6_21.
apply not_col_permutation_1.
apply H31.
4: apply col_permutation_2.
4: apply bet_col.
4: apply H33.
assumption.
Col.
Col.
eapply (proj3_col A C B A' C' B' P Q); auto.
subst BB.
Between.
induction(eq_dec_points C C').
subst C'.
apply between_symmetry.
eapply (proj_preserves_bet1 C B A _ _ P Q); try assumption.
Between.
assert(HH:=proj_diff_not_col_inv B A B' A' P Q H14 H1 H0).
destruct HH.
assert(HH:=proj_diff_not_col_inv B C B' C' P Q H14 H1 H2).
destruct HH.
assert(HH:= proj_one_side B A B' A' P Q H14 H1 H0).
induction HH.
assert(B' = A').
apply H17.
Col.
subst B'.
apply between_trivial2.
assert(HH:= proj_one_side B C B' C' P Q H14 H1 H2).
induction HH.
assert(B' = C').
apply H19.
Col.
subst B'.
apply between_trivial.
assert(HH:=proj_diff_not_col_inv B A B' A' P Q H14 H1 H0).
destruct HH.
assert(HH:=proj_diff_not_col_inv B C B' C' P Q H14 H1 H2).
destruct HH.
assert(TS B B' A C).
unfold TS.
repeat split.
intro.
assert(B' = A').
apply H23.
Col.
subst B'.
assert(Col A' B C).
ColR.
assert(A' = C').
apply H25.
Col.
contradiction.
intro.
assert(B' = C').
apply H25.
Col.
subst B'.
assert(Col C' A C).
ColR.
assert(C' = A').
apply H23.
ColR.
subst C'.
tauto.
exists B.
split; Col.
assert(TS B B' A' C).
eapply l9_8_2.
apply H26.
assumption.
assert(TS B B' C' A').
eapply l9_8_2.
apply l9_2.
apply H27.
assumption.
unfold TS in H28.
spliter.
ex_and H30 BB.
assert(BB= B').
eapply l6_21.
apply not_col_permutation_1.
apply H29.
4: apply col_permutation_2.
4: apply bet_col.
4: apply H31.
auto.
Col.
Col.
eapply (proj3_col A C B A' C' B' P Q); auto.
subst BB.
Between.
Qed.

(* Specifications: *)
Lemma one_side_eq_o : forall A B C D, A <> B -> OS A B C D -> eq_o A B C A B D.
intros.