how can X be continuously deformed to Y?
Let X be a ball , i.e., the interior of a circle (either a s astand-alone space, or
embedded in R^n), and let Y be, say, the center of the ball . Can you see how
to deform X into Y continuously.?. Can you see why, e.g., a circle could not be
deformed to a point (i.e., to a 1-pt. subspace of the circle.)?
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