## `Ax::canonicalUnitNormal` -- the axiom of canonically unit normals

#### Introduction

`Ax::canonicalUnitNormal` states that the method `"unitNormal"` of an integral domain (category `Cat::IntegralDomain`) returns a unique unit normal.

#### Generating the axiom

`Ax::canonicalUnitNormal()`

#### Details

- The axiom `Ax::canonicalUnitNormal` is used to state that the unit normals of an integral domain (category `Cat::IntegralDomain`) returned by the method `"unitNormal"` are unique.
- This means that for each non-zero element `x` of the integral domain there exists an unique associate among the associate class of `x`, i.e. for any `x` and `y` of a domain `dom` of category `Cat::IntegralDomain` where `dom::associates(x, y)` returns `TRUE` the equation `dom::equal(dom::unitNormal(x), dom::unitNormal(y)) = TRUE` must hold.
- Note that this axiom does not imply that the unit normals are canonically represented. The unit normals of `x` and `y` must be mathematically equal in the sense of the method `"equal"`, they need not be structurally equal as MuPAD objects.

#### Changes

- no changes

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