Is H ∩ K a Subgroup of G with Subgroups H and K?

In summary, for the given group G with subgroups H and K, in order for HintersectK to be a subgroup, H and K must satisfy the same properties as G, such as being closed, having identity elements, and having inverses. This can be shown by considering the elements of HintersectK and using the properties of H and K.
  • #1
kathrynag
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Homework Statement



Let G be a group with subgroups H and K. Prove HintersectK is a subgroup.

Homework Equations





The Attempt at a Solution


G is a group with subgroups H and K. Then H and K are closed, have identity elements in G and have inverses.
HintersectK is a subgroup because H and K must satisfy the same properties of G.
 
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  • #2
let [tex] a,b \epsilon H [/tex] and [tex] a,b \epsilon K [/tex].Then [tex] a*b \epsilon H [/tex] and [tex] a*b \epsilon K [/tex].Let [tex] a \epsilon H [/tex] and [tex] a \epsilon K [/tex].Then [tex] a^{-1} \epsilon H [/tex] and [tex] a^{-1} \epsilon K [/tex].
 
  • #3
that makes sense
 

1. What is a "group with subgroups proof"?

A "group with subgroups proof" is a mathematical proof that demonstrates the properties of a group, which is a set of elements with a defined operation that satisfies certain axioms. This proof specifically focuses on subgroups, which are subsets of the original group that also satisfy the axioms and have their own defined operation.

2. Why is the concept of subgroups important in group theory?

The concept of subgroups is important because it allows us to break down a larger group into smaller, more manageable parts. This can help us better understand the structure and properties of the original group, as well as make certain calculations and proofs easier to perform.

3. How do you prove that a subset is a subgroup of a given group?

To prove that a subset is a subgroup of a given group, you must show that it satisfies the four axioms of a group: closure, associativity, identity, and inverse. This can typically be done by showing that the subset is closed under the group's operation, that the operation is associative for elements within the subset, that the identity element of the group is also an element of the subset, and that every element in the subset has an inverse within the subset as well.

4. Can a group have multiple subgroups?

Yes, a group can have multiple subgroups. In fact, every group has at least two subgroups: the trivial subgroup containing only the identity element, and the entire group itself. However, a group can have an infinite number of subgroups, depending on the structure and properties of the group.

5. How do subgroups relate to other concepts in mathematics?

Subgroups are closely related to other concepts in mathematics, such as homomorphisms, isomorphisms, and normal subgroups. They are also used in many areas of mathematics, including algebra, number theory, and geometry. Additionally, the concept of subgroups is important in other fields such as physics and computer science.

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