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Let $X$ and $Y$ be (any) topological spaces. Show that the projection

$\pi_1$ : $X\times Y\to X$

is an open map.

  • 3
    How do you define the topology on $X\times Y$?2012-11-29
  • 4
    ProofWiki: [Projection from Product Topology is Open](http://www.proofwiki.org/wiki/Projection_from_Product_Topology_is_Open)2013-04-11

3 Answers 3