Imagining $S^1$ with antipodal points identified
6227
Showing diffeomorphism between $S^1 \subset \mathbb{R}^2$ and $\mathbb{RP}^1$
84686
Geometric Description Of a Set In The Complex Plane
44559
Finding a homeomorphism $\mathbb{R} \times S^1 \to \mathbb{R}^2 \setminus \{(0,0)\}$
130851
Squaring the plane, with consecutive integer squares. And a related arrangement
53261
Show that Pn is an (n+1)-dimensional subspace
77323
Existence of continuous angle function $\theta:S^1\to\mathbb{R}$
135980
Geometric interpretation of a complex set
119050
Fundamental group of $S^2$ with north and south pole identified
90056
A synthetic geometrical proof required on a result regarding Isosceles triangles.
127185
How to test whether a set of four points can form a parallelogram
147429
Set of points in $\mathbb{C}$ s.t. $z^{n-1} = \overline z$
37060
The Parallelogram Identity for an inner product space
79727
Direct proof of non-flatness
27933
Show that unit circle is not homeomorphic to the real line
27629
How to prove that $S^{2n+1}/S^1$ is homeomorphic to $\mathbb CP^n$ under a given identification
64993
Connectedness of the $S^2$ sphere
49040
Great-circle lines in Equirectangular projection