Is this ok to prove?

  • Thread starter semidevil
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  • #1
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so I need to show that in any group, it's elements and inverse has the same order.

so can I say that since it is a group, we know that there exists a unique inverse for each element. So each element would have 1 inverse. And then, that means we have the same number of elements as number of inverses?

does that work? or am I missing something?
 

Answers and Replies

  • #2
shmoe
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Can you state the definition of the order of an element in a group?
 
  • #3
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shmoe said:
Can you state the definition of the order of an element in a group?


so the order is the number of elements in a group....

is this suppose to be a hint? :)
 
  • #4
semidevil...

The order of an element g in a group G is n such that g^n = identity where n is the smallest positive integer >= 1. To prove an element and its inverse have the same order you can say:

g^n = identity
(g^-1) ^ n = (g^n)^-1 = (identity)^-1 = identity
 
  • #5
shmoe
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semidevil said:
so the order is the number of elements in a group....

That's the order of the group, not an element. I was hoping to get you to check the definition carefully;).
 
  • #6
Heh, sorry shmoe...didn't mean to steal your thunder.
 
  • #7
shmoe
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No thunder to be stolen, we're all here to help (or be helped) :smile:
 

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