Hello @Khallil !!
I want to show that the unit sphere cannot be covered by a single surface patch.
We have that the unit sphere is the closed set $\{(x,y,z)\in \mathbb{R}^3 \mid x^2+y^2+z^2=1\}$.
By the definition of the surface, this set must be homeomorphic to an open set in $\mathbb{R}^2$, but since the above set is closed that cannot be true.
Is this correct?