proposition: Lemma poly_coord {R : rcfType} (c : pair_vectType (regular_vectType R) (regular_vectType R)) (p : {poly R}) (t : R) : p.[t] *: c = c.1 * p.[t] *: (1, 0) + c.2 * p.[t] *: (0, 1).
proof: Proof. congr (_, _); rewrite /= !scaler0 ?addr0 ?add0r mulrC /GRing.scale /=; ring. Qed.
imports: mathcomp(all_ssreflect all_algebra all_real_closed reals) mathcomp.algebra_tactics(ring lra) casteljau convex counterclockwise intersection