For example, the first isomorphism theorem is a commutative triangle as follows:
Since f = h ^{o} φ, the left diagram is commutative; and since φ = k ^{o} f, so is the right diagram.
Similarly, the square above is commutative if y ^{o} w = z ^{o} x.
Commutativity makes sense for a polygon of any finite number of sides (including just 1 or 2), and a diagram is commutative if every polygonal subdiagram is commutative.
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