Library /sys$common/syshlp/basichelp.hlb ATN  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The ATN function returns the angle of a specified tangent, in  radians  or
  degrees  depending  upon  which  angle  clause  you choose with the OPTION
  statement.

  Example

  Angle_rad = ATN(1)

  Additional Information (explode) :

• Syntax