Let $D^2 = \{x\in \Bbb R^2: |x|\leq 1\}$ be the $2$-disc. A point can be in any space.
There is a unique $f$ from $D^2$ to the point, but how do we define a map from that point to the disk?
2026-03-30 05:32:02.1774848722
How to show a disk is homotopically equivalent to a point?
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