math:atan2

Returns the angle in radians subtended at the origin by the point on a plane with coordinates (x, y) and the positive x-axis, the result being in the range -π to +π. (Note the order of arguments (y, x). There are some maths libraries that implement an atan2 function with the arguments in the order (x, y).

atan2($y as xs:double, $x as xs:double) ➔ xs:double

Namespace

http://www.w3.org/2005/xpath-functions/math

Links to W3C specifications

XPath 3.1 Functions and Operators

XPath 4.0 Functions and Operators

Saxon availability

Available in XPath 3.0, XSLT 3.0, XQuery 3.0, and later versions. From Saxon 9.6, available in all editions. Available for all platforms.

Notes on the Saxon implementation

Implemented since Saxon 9.4; available whether or not XPath 3.0 is enabled. Saxon also (for compatibility) implements the function math:atan2() in namespace http://exslt.org/math.