G\K: Is G\K a Subgroup? | Index 2 Group and Subgroup K

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SUMMARY

The discussion centers on the question of whether the quotient group G/K is a subgroup when K is a subgroup of a group G with index 2. It is established that the elements of G/K are cosets of the form gK, which are not elements of G unless K is the trivial subgroup {e}. Therefore, G/K cannot be considered a subgroup of G under these conditions.

PREREQUISITES
  • Understanding of group theory concepts, specifically quotient groups.
  • Familiarity with the definition of subgroup and index of a subgroup.
  • Knowledge of cosets and their properties in group theory.
  • Basic comprehension of the trivial subgroup in group theory.
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  • Study the properties of quotient groups in group theory.
  • Learn about the implications of subgroup index in relation to group structure.
  • Explore the concept of cosets and their role in defining group operations.
  • Investigate examples of groups with index 2 and their subgroups.
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Mathematicians, students of abstract algebra, and anyone studying group theory who seeks to deepen their understanding of subgroup properties and quotient groups.

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Lets say I have a group of index 2 and I have some subgroup K. Is it that G\K is a subgroup as well?
 
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Punkyc7 said:
Lets say I have a group of index 2 and I have some subgroup K. Is it that G\K is a subgroup as well?

That's not the sloppiest question I've ever seen posted but it's right up there. Can you rephrase that?
 
Last edited:
elements of G/K are cosets gK, these are not elements of G unless K = {e}.
 

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