> Additionally, why should we
> culturally prioritize the Cartesian decomposition over other
decompositions
> (such as radius-angle decomposition)?

One reason: we are using "ka'o" which does this. If we wanted a different
decomposition, we could use something else (such as "ka'o'ei").

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It should be noted, though, that there are other ways to express imaginary
numbers than just these two. For example, there is a certain structure on a
certain set of matrices which is isomorphic with C.