Converts x
to a double and returns its arc tangent in radians.
Returns a value in the range -PI/2..PI/2, or NaN if x
is NaN.
external double atan(num x);
© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/2.0.0/dart-math/atan.html