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Closed Sets In The Plane

TOPO-VKCKXE

Consider the real plane $\mathbb{R}^2$ equipped with the standard (metric) topology.

Which of the following subsets are closed? Select ALL that apply.

A

$\{(x,y)\in\mathbb{R}^2 : x^2+y^2<1\}$

B

$\{(x,y)\in\mathbb{R}^2 : x^2+y^2\leq 1\}$

C

$\{(1,2), (\pi, 7)\}$

D

$\{(x,y)\in\mathbb{R}^2 : x=y\}$

E

$\{(x,y)\in\mathbb{R}^2 : x < y \}$