Talk:Euclidean group

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In a math class a question arose that was very difficult. The question read. Let 'a' be a line an 'b'=(A,alpha). Prove that angle(a,b)=alpha. This question has caused me many problems and I was hoping that some one would be able to clearify if with me. Thank you if there are any ideas please send them to rupert41@hotmail.com

[edit] Inversion with respect to a point in 3D

How come "inversion with respect to a point" is "not preserving orientation" in 3D? BTW what it means to preserve orientation in 3D? --TMa

[edit] Improvements

I've done some work on the ordering of sections, and other tweaks. It shouldn't be too hard to put this into approved 'concentric' style. Charles Matthews 15:35, 13 October 2006 (UTC) OK, that should be somewhat better now. The only point of real concern I have is this: does the article really need the non-closed subgroups enumerated? I would have thought the closed subgroups were enough. Charles Matthews 15:52, 13 October 2006 (UTC)

If the overview is restricted to closed subgroups this has to be mentioned, you cannot say the subgroups are all of type A, B, or C, when there is also a type D. However, to clarify the restriction you have to explain it, so you end up briefly explaining the additional kind anyway.--Patrick 22:08, 13 October 2006 (UTC)

I don't agree: if it is thought of as a topological group, why not just explain the closed subgroups? I don't see the need for any more than that. Charles Matthews 12:23, 14 October 2006 (UTC)

I was thinking of the algebraic concept of a group. The concept of a topological subgroup seems more complex.--Patrick 23:39, 14 October 2006 (UTC)