- #1
Philip2016
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Homework Statement
I need to prove that the unit n-sphere is a closed C^inf-manifold, and am not sure what to do.
Homework Equations
The unit n-sphere is defined as:
S^n = {(x_0,...,x_n) belongs to R^(n+1) | (x_0)^2+...+(x_n)^2=1}
The Attempt at a Solution
It's not a proof, but a simple example of transfering any point x of distance r to origo on the spherical coordinate system to the unit n-sphere, through the infinetly differentiable function 1/r. But this is no proof, just an example. How do I prove that a certain manifold is 1) closed/opened (has/doesn't have boundary, i.e. delta M = the zero set), 2) topological/smooth/C^k?
Thanks in advance for any help.