Returns the arc tangent of the argument, the result being in the range -
atan($arg as xs:double?) ➔ xs:double?
The supplied angle in radians
Links to W3C specifications
Available in XPath 3.0, XSLT 3.0, XQuery 3.0, and later versions. From Saxon 9.6, available in all editions.
Notes on the Saxon implementation
Implemented since Saxon 9.3; available whether or not XPath 3.0 is enabled. Saxon also
(for compatibility) implements the function math:atan() in namespace