# Talk:Chain duality III (Ex)

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Revision as of 11:34, 1 June 2012 by Martin Olbermann (Talk | contribs)

We check this for objects .

Let be an element of .

We have to check the equality of

and

This follows from the commutative diagram

as the first square commutes by naturality of and the second one by definition of a functor of categories with chain duality.