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I work in population dynamics. I want to show somewhere in my work that the $h-$th power of every element in a finite group of order $h$ is the identity element of the group. I guess this is elementary result but it would be nice if somebody show me how to do it or where to find it. Thanks

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The order of every element of a group is a divisor of $h$ by Lagrange's Theorem. So if $x$ is an element of your group of order $k$ then $h = k\cdot l$ for some $l.$ Hence we have

$$x^h = x^{k\cdot l} = (x^k)^l = (e)^l = e.$$

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    Can you provide a name of a book where I read this result for citation purpose.2012-11-29
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    @zizo abstract algebra by dummit and foote2012-11-29
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    @jim I can't open this book from google :-(.2012-11-29
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    Why exactly do you need to cite this theorem? One reason a theorem has a name is so that you can reference to it :)2012-11-29
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    Okay, thanks. I am master's student, I didn't know this.2012-11-29
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    I thought that a person must show where he find the result from.2012-11-29
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    Sure but usually if something has a name as known as this one then you don't cite the result. In a way the name by itself is the citation2012-11-29