English
The interval Icc x y carries a smooth manifold structure compatible with the two-chart atlas, for any level of smoothness.
Русский
Интервал Icc x y несёт гладкую структуру манифольда, совместимую с атласом из двух чартов, для любого уровня гладкости.
LaTeX
$$IsManifold\ (modelWithCornersEuclideanHalfSpace 1)\ (Set.Icc x y).Elem$$
Lean4
theorem contDiffOn_stereoToFun {n : WithTop ℕ∞} : ContDiffOn ℝ n (stereoToFun v) {x : E | innerSL _ v x ≠ (1 : ℝ)} :=
by
refine ContDiffOn.smul ?_ (ℝ ∙ v)ᗮ.orthogonalProjection.contDiff.contDiffOn
refine contDiff_const.contDiffOn.div ?_ ?_
· exact (contDiff_const.sub (innerSL ℝ v).contDiff).contDiffOn
· intro x h h'
exact h (sub_eq_zero.mp h').symm