Finding the number of elements in a cyclic group

  • Context: Undergrad 
  • Thread starter Thread starter hitmeoff
  • Start date Start date
  • Tags Tags
    Cyclic Elements Group
Click For Summary

Discussion Overview

The discussion focuses on finding the number of elements in a cyclic subgroup generated by an element within a group, specifically examining the subgroup Z30 generated by the element 25. The scope includes mathematical reasoning and clarification of group operations.

Discussion Character

  • Mathematical reasoning, Conceptual clarification

Main Points Raised

  • One participant questions the number of elements in the subgroup generated by 25 in Z30, initially proposing that it should contain {0, 1, 5, 25}.
  • Another participant clarifies that the operation in Z30 is addition, indicating that the subgroup elements must be generated through addition modulo 30.
  • A subsequent reply provides a detailed calculation of the elements generated by repeated addition of 25, concluding that the correct elements are indeed 0, 5, 10, 15, 20, and 25, totaling six elements.
  • A final post expresses gratitude for the clarification, indicating a misunderstanding of the text and the operations involved.

Areas of Agreement / Disagreement

Participants do not appear to disagree on the final count of elements in the subgroup, but there was initial confusion regarding the correct elements and the method of generation.

Contextual Notes

The discussion highlights a potential misunderstanding of group operations and the generation of elements, which may depend on the clarity of definitions and operations in the context of cyclic groups.

hitmeoff
Messages
260
Reaction score
1
How do we go about finding the number of elements of a cyclic subgroup that's generated by an element in the main group. For example:

The subgroup Z30 generated by 25.

I would think this subgroup would be {0,1,5,25} but there's supposed to be 6 elements and not four. Whats going on?
 
Physics news on Phys.org
The operation in Z30 is addition, so your subgroup elements need to be generated by addition (for example, 25 + 25 = 20 (mod 30) must be in your subgroup).
 
hitmeoff said:
How do we go about finding the number of elements of a cyclic subgroup that's generated by an element in the main group. For example:

The subgroup Z30 generated by 25.

I would think this subgroup would be {0,1,5,25} but there's supposed to be 6 elements and not four. Whats going on?
How did you get that? 25+ 25= 50= 20 (mod 30). 25+ 25+ 25= 75= 15 (mod 30). 25+ 25+ 25+ 25= 100= 10 (mod 30). 25+ 25+ 25+ 25+ 25= 125= 5 (mod 30). 25+25+ 25+ 25+ 25+ 25= 150= 0 (mod 50). 25+25+ 25+ 25+ 25+ 25+ 25= 175= 25 (mod 30). Those are your 6 elements.
 
Thanks a lot guys. I guess I was just having a hard time reading my text and certain things weren't clear, I was confusing things.

You guys cleared it up.
 

Similar threads

  • · Replies 38 ·
2
Replies
38
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 7 ·
Replies
7
Views
5K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 1 ·
Replies
1
Views
985
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 13 ·
Replies
13
Views
2K
Replies
4
Views
2K