FUNDAMENTAL THEOREM ON HOMOMORPHISMS

In abstract algebra, the 'fundamental theorem on homomorphisms', also known as the 'fundamental homomorphism theorem', relates the structure of two objects between which a homomorphism is given, and of the kernel and image of the homomorphism.
The homomorphism theorem is used to prove the isomorphism theorems.

Contents
Group theoretic version
Other versions
See also
External links

Group theoretic version


Given two groups ''G'' and ''H'' and a group homomorphism ''f'' : ''G''→''H'', let ''K'' be a normal subgroup in ''G'' and φ the natural surjective homomorphism ''G''→''G''/''K''. If ''K'' ⊂ ker(''f'') then there exists a unique homomorphism ''h'':''G''/''K''→''H'' such that ''f'' = ''h'' φ.
The situation is described by the following commutative diagram:
By setting ''K'' = kernel(''f'') we immediately get the first isomorphism theorem.

Other versions


Similar theorems are valid for monoids, vector spaces, modules, and rings.

See also



Quotient category

External links



A proof at planetmath

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