Show that each point of closed submanifold $\mathbb R^{n+2}$ have “tangent line” in $\mathbb R^{n+2}$
90970
How to prove the line exist?
49845
For an ellipse with minor radius $b$, show that the product of distances from the foci to any tangent line is $b^2$
132311
T$\mathbb{S}^{n} \times \mathbb{R}$ is diffeomorphic to $\mathbb{S}^{n}\times \mathbb{R}^{n+1}$
110691
Proving that given any two points in a connected manifold, there exists a diffeomorphism taking one to the other
108687
Open subsets in a manifold as submanifold of the same dimension?
115272
Showing that projections $\mathbb{R}^2 \to \mathbb{R}$ are not closed
125212
How to Show that the Only Subspaces of $R^2$ are the zero subspace, $R^2$ itself, and the lines through the origin
33734
Every closed subset $E\subseteq \mathbb{R}^n$ is the zero point set of a smooth function
27366
Prove that $g$ is tangent to the graph of $f$
67287
Visible seams on tangent normal maps
47975
Closed cone in the euclidean space $\mathbb{R}^n$
2348
Show that the sphere, S, and $\mathbb{R}^2$ is not homeomorphic
64523
interior points and limit points of $\{(x,y): x^2+2y^2 < 1\}$
151981
Tangent line of a convex function
154496
Proving that the Hopf map $S^3 \to S^2$ is a submersion
23414
Topologist's Sine Curve: A rigorous proof of why $\overline{S} = S \cup V$
36099
Show that $\|f\|^{2}$ attains a minimum value on the interior of $B$