Talk:Binary tetrahedral group

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[edit] binary polyhedral groups

If I've understood this right, all the binary polyhedral groups (i.e. binary cyclic, b. dicyclic, b. tetrahedral, b. octahedral, b. Icosahedral) have exactly one element of order 2. If I am right, this seems to me (A) probably connected with the name "binary", and (B) worth mentioning in the article. Maproom (talk) 11:40, 14 February 2008 (UTC)

This is correct since all the binary polyhedral groups are subgroups of the unit quaternions containing −1 which is the unique involution in that group. I believe, however, that the adjective "binary" comes from the fact that these groups are double covers of the ordinary polyhedral groups and not from the presence of a unique involution. -- Fropuff (talk) 22:18, 14 February 2008 (UTC)