diff --git a/src/content/3.11/kan-extensions.tex b/src/content/3.11/kan-extensions.tex index 7d927bdd8..5f502221c 100644 --- a/src/content/3.11/kan-extensions.tex +++ b/src/content/3.11/kan-extensions.tex @@ -336,13 +336,13 @@ \section{Kan Extensions as Ends} We can use the product-exponential adjunction: \[\int_a \int_i \Set(\cat{A}(K i, a),\ (F' a)^{D i})\] The exponential is isomorphic to the corresponding hom-set: -\[\int_a \int_i \Set(\cat{A}(K i, a),\ \cat{A}(D i, F' a))\] +\[\int_a \int_i \Set(\cat{A}(K i, a),\ \Set(D i, F' a))\] There is a theorem called the Fubini theorem that allows us to swap the two ends: -\[\int_i \int_a \Set(\cat{A}(K i, a),\ A(D i, F' a))\] +\[\int_i \int_a \Set(\cat{A}(K i, a),\ \Set(D i, F' a))\] The inner end represents the set of natural transformations between two functors, so we can use the Yoneda lemma: -\[\int_i \cat{A}(D i, F' (K i))\] +\[\int_i \Set(D i, F' (K i))\] This is indeed the set of natural transformations that forms the right hand side of the adjunction we set out to prove: \[[\cat{I}, \Set](D, F' \circ K)\]