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##### 3.1.4.2 Unary forms

Unary or one-operand forms are summarized in the following table, where `X` stands for the operand.

Op | Operand | Result | Description
--- | --- | --- | ---
`-X` | scalar | scalar | Unary scalar negation.
`-X` | vector | vector | Unary vector negation.
`|X|` | vector | scalar | Vector length.
`unit(X)` | vector | vector | Unit vector with same direction.
`sqrt(X)` | scalar | scalar | Scalar square root.
`sin(X)` | scalar | scalar | Trigonometric sine (`X` in degrees).
`cos(X)` | scalar | scalar | Trigonometric cosine (`X` in degrees).
`atan2(X,Y)` | scalar | scalar | Polar angle in degrees of vector [X,Y].
`inverse(X)` | transform | transform | Inverse transform.

Errors are reported when `|X|`, `unit`, `sqrt`, `atan2`, and `inverse` fail due to bad parameters.