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WikiProject Mathematics (Rated Start-class, Mid-importance)
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Mathematics rating:
Start Class
Mid Importance
 Field: Algebra

Proper subgroup[edit]

Is a trivial subgroup a proper subgroup? The article says so but my text says otherwise. -- Taku 23:07, 8 October 2005 (UTC)

I think it is the same as with a set. A proper subset Y of X is a subset Y which does not equal X. So, unless the group is trivial to start with, its trivial subgroup must be proper. No? Oleg Alexandrov (talk) 00:09, 9 October 2005 (UTC)
I think I have seen both, but what Oleg writes is what I would guess is the most common. It needs a survey of recent literature. People write "non-trivial proper subgroup" when they want to make sure there is no misunderstanding. --Zero 11:07, 10 October 2005 (UTC)

Umm the group used in the example is certaintly NOT cyclic. —Preceding unsigned comment added by (talk) 16:47, 30 March 2008 (UTC)

No, it is. The element 1 generates the group.

Topology Expert (talk) 04:10, 10 October 2008 (UTC)

subgroup vs. uninion[edit]

Given 2 group, can we always union them and get a new group? so both 2 groups are subgroup of the new group? Jackzhp (talk) 04:10, 8 April 2011 (UTC)

The union of two groups isn't a group (unless one of the two is a subgroup of the other). The direct product may be what you're looking for. --Zundark (talk) 09:24, 8 April 2011 (UTC)