Definition Side1 : Triangle -> Segment.Definition Side2 : Triangle -> Segment.

(* Specifications: *)
Theorem auxs1 : forall t : Triangle, origin (base t) = extremity (Side1 t).
Theorem auxs2 : forall t : Triangle, extremity (base t) = extremity (Side2 t).
Theorem auxs3 : forall t : Triangle, summit t = origin (Side1 t).
Theorem auxs4 : forall t : Triangle, summit t = origin (Side2 t).
Theorem thm4_3c : forall t : Triangle, DiLn (ln (base t)) (ln (Side1 t)).
Theorem thm4_3d : forall t : Triangle, DiLn (ln (base t)) (ln (Side2 t)).