Show the dihedral group ##D_6## is isomorphic to ##S_3 x Z_2##

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SUMMARY

The dihedral group ##D_6## is isomorphic to the direct product of the symmetric group ##S_3## and the cyclic group ##Z_2##. Both groups contain 12 elements, with specific orders for each element outlined in the discussion. The correspondence between elements of ##S_3 \times Z_2## and ##D_6## can be established by matching elements while preserving their orders. The discussion emphasizes using generators and relations for clarity in group representation.

PREREQUISITES
  • Understanding of group theory concepts, particularly dihedral groups and symmetric groups.
  • Familiarity with the notation and operations of groups, including generators and relations.
  • Knowledge of the orders of elements in groups, specifically for ##S_3## and ##Z_2##.
  • Basic understanding of isomorphism in the context of abstract algebra.
NEXT STEPS
  • Study the structure and properties of dihedral groups, focusing on ##D_6##.
  • Learn about symmetric groups, particularly the permutations in ##S_3##.
  • Explore the concept of group isomorphism and how to establish correspondences between groups.
  • Investigate the use of generators and relations in group theory for clearer representations.
USEFUL FOR

Mathematicians, students of abstract algebra, and anyone interested in group theory, particularly those studying symmetry and isomorphisms in algebraic structures.

Robb
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Homework Statement
Show that the dihedral group ##D_6 is isomorphic to ##S_3 x Z_2## by constructing an explicit isomorphism. ( Hint: Color every other vertex of a hexagon red. Which elements of ##D_6## permute these 3 vertices. Also, which elements are order 2?)
Relevant Equations
##S_3 = { e, f, g, f^2, gf, gf^2 }##
##Z_2 = { 0,1 }##
##D_6 = { e, r, r^2, r^3, r^4, r^5, s, sr, sr^2, sr^3, sr^4, sr^5 }##
##f^3 = e##
##g^2 = e##
I'm not really sure where to begin with this problem. Any insight as to where to begin or what to look out for would be much appreciated!

Orders of ##S_3##
##|e|=1##
##|f|=3##
##|f^2|=2##
##|g|=2##
##|gf|=2##
##|gf^2|=3##

Orders of ##Z_2##
##|0|=1##
##|1|=2##

Orders of ##S_3 x Z_2##
##|e,0|=1##
##|e,1|=2##
##|f,0|=2##
##|f,1|=2##
##|f^2,0|=2##
##|F^2,1|=6##
##|g,0|=2##
##|g,1|=6##
##|gf,0|=3##
##|gf,1|=2##
##|gf^2,0|=2##
##|gf^2,1|=2##

Orders of ##D_6##
##|e|=1##
##|r|=6##
##|r^2|=3##
##|r^3|=2##
##|r^4|=3##
##|r^5|=6##
##|s|=2##
##|sr|=2##
##|sr^2|=2##
##|sr^3|=2##
##|sr^4|=2##
##|sr^5|=2##
 
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What is ##D_6##? I'm asking since there are various definitions for it. The coloring hint indicates it is the symmetry group of a hexagon, the representation you gave under Relevant Equations indicates that you can use generators and relations, too.

Furthermore I would write ##S_3## explicitly with permutations rather than with ##e,f,g##, but that's only a side note. ##S_3=\langle e,f,g\,|\,e=f^3=g^2 \rangle## works as well. I also would choose only one group operation. As you have chosen the multiplication for ##D_6## and ##S_3##, let's do the same with ##\mathbb{Z}_2=\{\,-1,+1\,\}##.

Now ##S_3 \times \mathbb{Z}_2## as a set are all pairs ##(\sigma,\varepsilon)## with ##\sigma\in S_3## and ##\varepsilon \in \mathbb{Z}_2##. These are ##12## pairs total, same as ##12## elements you listed for ##D_6##. Have you tried to establish a correspondence between them? And if possible by keeping the orders of the elements!
 

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