Is t*x = x*t^(-1) for Elements of Order 2 in Any Group?

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Discussion Overview

The discussion revolves around the relationship between elements of order 2 in a group, specifically examining the equation t*x = x*t^(-1) where t = xy for elements x and y of order 2. The scope includes theoretical exploration and mathematical reasoning.

Discussion Character

  • Exploratory
  • Mathematical reasoning

Main Points Raised

  • One participant proposes to prove that if t = xy, then t*x = x*t^(-1) using properties of elements of order 2.
  • The same participant notes that since |x| = 2 and |y| = 2, it follows that (xy)^2 = 1, indicating that t also has order 2.
  • Another participant identifies t^(-1) as y*x and provides a verification of this relationship through group operations.
  • A later reply confirms the relationship by showing that t^-1 = yx and demonstrates that tx = xyx, asserting their equality.

Areas of Agreement / Disagreement

Participants appear to agree on the relationships derived from the properties of elements of order 2, but the initial proof and derivation of t^n = (xy)^n remains unresolved.

Contextual Notes

The discussion includes assumptions about the properties of group elements and their orders, but does not resolve the derivation of t^n = (xy)^n from the established conditions.

xsw001
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Let x, y be elements of order 2 in any group G.
Prove that if t = xy, then t*x = x*t^(-1)

Here is what I got so far.
Proof:
Since |x| = 2 => x^2 = 1; |y| = 2 => y^2 = 1, then (x^2)(y^2) = 1 => (xy)^2 = 1
Suppose t = xy, then t^2 = (xy)^2 = 1
WTS (want to show) t*x = x*t^(-1)

This group looks like Dihedral group D2n, the operation t*x = x*t^(-1) similar to r*s = s*r^(-1),
we know r^n = s^2 = 1 in D2n, since x^2 = 1, we can let x = s, so x^2 = s^2 = 1. Hence we've shown x = s,
Now I need to show t^n = (xy)^n = 1 so that I can let t = xy = r,
and if we show t = xy = r, then we get exactly the same operation in D2n such that r*s = s*r^(-1) where r = t = xy and s = x

Here is what I stuck, how do I show t^n=(xy)^n=1 ? I only know t^2 = (xy)^2 = 1 from the given condition. Now I need to derive from there and to show that t^n = (xy)^n

Any suggestions?

BTW, I think that I post in the wrong session. I'll make a note next time since I can't delete the post.
 
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Notice that t^{-1}=y*x because t*(y*x)=(t*y)*x=(x*(y*y))*x=(x*1)*x=1and similarly (y*x)*t=1.
 
Yes! Got it!
Since t^-1=(y^-1)*(x^-1) and x^2=1 => x=x^-1, y^2=1 => y=y^-1, so t^-1=yx
Then tx=xyx, and x(t^-1)=xyx, indeed they are equal!
Thanks for the tips Delta! Now it seems so simple!
 
Last edited:

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