Modern Algebra Factor Groups question

In summary, the conversation discusses a solution to a problem involving normal subgroups and group orders. The solution involves using the fact that K is normal in G and that |g| = n for some g in G. It is suggested that taking Kg to the nth power will result in the identity, and therefore the order of Kg must divide n. However, the speaker realizes they may be missing something, potentially related to the fact that K is normal in G.
  • #1
PsychonautQQ
784
10

Homework Statement


If K is normal in G and |g| = n for some g in G, show that the order of Kg in G/K divides n.

Homework Equations


None

The Attempt at a Solution


Okay so I feel like I have a solution but I don't use all the information given so I'm trying to find holes in it...

g^n = 1

K = Kg^n = (Kg)^n. So it seems If we take Kg to the nth power we get it's identity. This means that the order of Kg must divide n.

What am I missing here?
 
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  • #2
PsychonautQQ said:

Homework Statement


If K is normal in G and |g| = n for some g in G, show that the order of Kg in G/K divides n.

Homework Equations


None

The Attempt at a Solution


Okay so I feel like I have a solution but I don't use all the information given so I'm trying to find holes in it...

g^n = 1

K = Kg^n = (Kg)^n. So it seems If we take Kg to the nth power we get it's identity. This means that the order of Kg must divide n.

What am I missing here?

If you mean you aren't using that K is normal in G, you need that fact to justify saying (Kg)^n=Kg^n, or even that G/K is a group. Better review why.
 

Related to Modern Algebra Factor Groups question

1. What is a factor group in modern algebra?

A factor group, also known as a quotient group, is a mathematical group that is formed by taking a subgroup of a larger group and "factoring out" the elements in that subgroup to form a new group. The elements in the factor group are the cosets of the subgroup, and the operation in the factor group is defined by the operation of the larger group.

2. How is a factor group different from a subgroup?

A subgroup is a subset of a group that also forms a group under the same operation. A factor group, on the other hand, is formed by taking a subgroup and "factoring out" its elements to create a new group. In other words, a subgroup is a smaller group within a larger group, while a factor group is a new group formed from the larger group and a subgroup.

3. What is the significance of factor groups in modern algebra?

Factor groups are important in modern algebra because they allow us to study the structure of a group by looking at its subgroups. By factoring out certain elements, we can simplify the group and gain a better understanding of its properties. Factor groups are also used in various applications, such as in cryptography and coding theory.

4. How do you determine the order of a factor group?

The order of a factor group is equal to the index of the subgroup being factored out. In other words, it is the number of distinct cosets in the factor group. This can be calculated by dividing the order of the larger group by the order of the subgroup.

5. What are some real-life examples of factor groups?

Factor groups can be found in various areas of mathematics and science. For example, in chemistry, the symmetry of molecules can be represented by factor groups. In computer science, error-correcting codes can be represented by factor groups. In physics, the symmetry of physical systems can also be described using factor groups.

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