End METRIC.
Section ANGLES.
Parameter AS : Set.
Parameter Angle : Point -> Point -> Point  -> AS.

Axiom SumAngles : forall A B C D E : Point,
Clockwise A B C ->
Clockwise A C D ->
Clockwise A D E ->
Angle B A C = Angle A C D ->
Angle D A E = Angle A D C ->
Between B A E.