Difference between revisions of "First group isomorphism theorem"

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{{Infobox
 
{{Infobox
 
|title=<span style="font-size:0.85em;">First isomorphism theorem</span>
 
|title=<span style="font-size:0.85em;">First isomorphism theorem</span>
|above=<span style="font-size:1.3em;">{{M|1=\begin{xy}\xymatrix{A \ar[r]^\varphi \ar[d]_{\pi} & B \\ A/\text{Ker}(\varphi) \ar@{.>}[r]^-{\theta}& \text{Im}(\varphi) \ar@{^{(}->}[u]^i }\end{xy} }}</span><br/>Where {{M|\theta}} is an [[group isomorphism|isomorphism]].
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|above=<div style="overflow:hidden;"><span style="font-size:1.3em;">{{M|1=\begin{xy}\xymatrix{A \ar[r]^\varphi \ar[d]_{\pi} & B \\ A/\text{Ker}(\varphi) \ar@{.>}[r]^-{\theta}& \text{Im}(\varphi) \ar@{^{(}->}[u]^i }\end{xy} }}</span></div>Where {{M|\theta}} is an [[group isomorphism|isomorphism]].
 
|header1=Properties
 
|header1=Properties
 
|data1=something
 
|data1=something

Revision as of 17:47, 16 July 2016

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Note:
First isomorphism theorem
[ilmath]\begin{xy}\xymatrix{A \ar[r]^\varphi \ar[d]_{\pi} & B \\ A/\text{Ker}(\varphi) \ar@{.>}[r]^-{\theta}& \text{Im}(\varphi) \ar@{^{(}->}[u]^i }\end{xy}[/ilmath]
Where [ilmath]\theta[/ilmath] is an isomorphism.
Properties
something

Statement

Let [ilmath](G,*)[/ilmath] and [ilmath](H,*)[/ilmath] be groups. Let [ilmath]\varphi:G\rightarrow H[/ilmath] be a group homomorphism, then[1]:

  • [ilmath]G/\text{Ker}(\varphi)\cong\text{Im}(\varphi)[/ilmath]
    • Explicitly we may state this as: there exists a group isomorphism between [ilmath]G/\text{Ker}(\varphi)[/ilmath] and [ilmath]\text{Im}(\varphi)[/ilmath].

Note: the special case of [ilmath]\varphi[/ilmath] being surjective, then [ilmath]\text{Im}(\varphi)=H[/ilmath], so we see [ilmath]G/\text{Ker}(\varphi)\cong H[/ilmath]

Proof

Notes

References

  1. Abstract Algebra - Pierre Antoine Grillet