Top network posts

• 13 Is it possible that $(ab)^{-1}$ is defined although $a^{-1},b^{-1}$ are not?
• 9 Every infinite Hausdorff space has an infinite discrete subspace
• 8 how to prove $f^{-1}(B_1 \cap B_2) = f^{-1}(B_1) \cap f^{-1}(B_2)$
• 7 Union of ascending chain of Topologies
• 6 Example of a ring satisfying this variant definition of "symmetric" on nilpotent elements
• 6 Compactness and Hausdorffness
• 6 Showing a function bijective
• View more network posts →