Inverse of Group Elements: Find g_i^-1g_j^-1

In summary, we are trying to find the inverse of ##(g_ig_j)## in a group ##G##. By using the relation for matrices, we can write the inverse as ##g_j^{-1}g_i^{-1}##. To verify this, we need to check if this satisfies the properties of the inverse for the element ##g_i g_j##.
  • #1
LagrangeEuler
717
20

Homework Statement


Find ##(g_ig_j)^{-1}## for any two elements of group ##G##.



Homework Equations


For matrices ##(AB)^{-1}=B^{-1}A^{-1}##



The Attempt at a Solution


I'm not sure how to show this? I could show that for matrices ##(AB)^{-1}=B^{-1}A^{-1}##. And that for numbers
##(ab)^{-1}=a^{-1}b^{-1}##
 
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  • #2
Hi LagrangeEuler! :smile:
LagrangeEuler said:
Find ##(g_ig_j)^{-1}## for any two elements of group ##G##.

If h = ##(g_ig_j)^{-1}##, then ##hg_ig_j## = I.

Sooo what combinations of gs would h have to be made of? :wink:
 
  • #3
Could I just write from that relation that ##(g_ig_j)^{-1}=g_j^{-1}g_i^{-1}##? :)
It looks obvious but what is right mathematical way to write it? :)
 
  • #4
LagrangeEuler said:
Could I just write from that relation that ##(g_ig_j)^{-1}=g_j^{-1}g_i^{-1}##? :)
It looks obvious but what is right mathematical way to write it? :)
Check whether it satisfies the properties of the inverse. If ##h## is the inverse of ##g##, then ##hg = gh = 1##. See if your ##h## satisfies this for ##g = g_i g_j##.
 

FAQ: Inverse of Group Elements: Find g_i^-1g_j^-1

What is the inverse of a group element?

The inverse of a group element g is the element g^-1 such that g * g^-1 = e, where e is the identity element of the group.

How do you find the inverse of a group element?

To find the inverse of a group element g, you can use the formula g^-1 = g^n-1, where n is the order of the group. Alternatively, you can use the inverse property, which states that g^-1 = g^(n-1), where n is the order of g.

What is the purpose of finding the inverse of group elements?

The inverse of group elements is useful in solving mathematical equations involving group operations. It also allows us to identify which elements are inverses of each other and to make predictions about the behavior of group elements.

Can all group elements have an inverse?

No, not all group elements have an inverse. Only elements that are invertible have an inverse. Invertible elements are those that have a multiplicative inverse, meaning they can be multiplied by another element to equal the identity element of the group.

Is the inverse of a group element unique?

Yes, the inverse of a group element is unique. This means that for a given group element g, there is only one element g^-1 that satisfies the definition of an inverse. In other words, every element has a unique inverse within a group.

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