Discrete Mathematics - Vol 3 | 15. Subgroups by Abraham | Learn Smarter
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15. Subgroups

The chapter introduces the concept of subgroups within the context of group theory, outlining the definitions, properties, and important theorems such as Lagrange's theorem. It details methods to determine whether a subset is a subgroup, explores cyclic subgroups, and discusses the significance of left and right cosets in relation to subgroup equivalency. Furthermore, the chapter highlights the implications of Lagrange's theorem for finite groups, including relationships between the orders of subgroups and their parent groups.

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Sections

  • 15.1

    Discrete Mathematics

    This section introduces subgroups in the context of group theory, defining what constitutes a subgroup and discussing properties and theorems related to them.

  • 15.2

    Subgroups

    This section introduces the concept of subgroups, their properties, and applications, including Lagrange’s theorem.

  • 15.2.1

    Definition Of Subgroups

    This section introduces the definition and characterization of subgroups in abstract algebra, emphasizing essential properties and Lagrange's theorem.

  • 15.2.2

    Characterization For Subgroups

    This section introduces the definition of subgroups in abstract groups and presents a characterization for verifying whether a subset is a subgroup.

  • 15.2.3

    Corollary On Finite Groups

    The section discusses the definition and characterization of subgroups, particularly in the context of finite groups, highlighting Lagrange’s theorem.

  • 15.2.4

    Generating Cyclic Subgroups

    This section introduces the concept of cyclic subgroups and the characterization of subgroups in groups, essential for understanding group structures in abstract algebra.

  • 15.2.5

    Cosets

    Cosets are defined as the collections formed by multiplying a fixed group element with a subgroup, with left and right cosets being specific variations based on the order of multiplication.

  • 15.2.6

    Lagrange's Theorem

    This section introduces Lagrange's Theorem, highlighting its significance in group theory, particularly regarding the relationship between a group's order and its subgroups.

References

ch64.pdf

Class Notes

Memorization

What we have learnt

  • A subgroup, formed from a s...
  • Lagrange's theorem states t...
  • Left and right cosets help ...

Final Test

Revision Tests