gcc/fortran/doc/gfortran/intrinsic-procedures/atan.rst

   1 ..
   2   Copyright 1988-2022 Free Software Foundation, Inc.
   3   This is part of the GCC manual.
   4   For copying conditions, see the copyright.rst file.
   5
   6 .. _atan:
   7
   8 .. index:: ATAN
   9
  10 .. index:: DATAN
  11
  12 .. index:: trigonometric function, tangent, inverse
  13
  14 .. index:: tangent, inverse
  15
  16 ATAN --- Arctangent function
  17 *****************************
  18
  19 .. function:: ATAN(X)
  20
  21   ``ATAN(X)`` computes the arctangent of :samp:`{X}`.
  22
  23   :param X:
  24     The type shall be ``REAL`` or ``COMPLEX`` ;
  25     if :samp:`{Y}` is present, :samp:`{X}` shall be REAL.
  26
  27   :param Y:
  28     The type and kind type parameter shall be the same as :samp:`{X}`.
  29
  30   :return:
  31     The return value is of the same type and kind as :samp:`{X}`.
  32     If :samp:`{Y}` is present, the result is identical to ``ATAN2(Y,X)``.
  33     Otherwise, it the arcus tangent of :samp:`{X}`, where the real part of
  34     the result is in radians and lies in the range
  35     -\pi/2 \leq \Re \atan(x) \leq \pi/2.
  36
  37   Standard:
  38     Fortran 77 and later, for a complex argument and for two arguments
  39     Fortran 2008 or later
  40
  41   Class:
  42     Elemental function
  43
  44   Syntax:
  45     .. code-block:: fortran
  46
  47       RESULT = ATAN(X)
  48       RESULT = ATAN(Y, X)
  49
  50   Example:
  51     .. code-block:: fortran
  52
  53       program test_atan
  54         real(8) :: x = 2.866_8
  55         x = atan(x)
  56       end program test_atan
  57
  58   Specific names:
  59     .. list-table::
  60        :header-rows: 1
  61
  62        * - Name
  63          - Argument
  64          - Return type
  65          - Standard
  66
  67        * - ``ATAN(X)``
  68          - ``REAL(4) X``
  69          - ``REAL(4)``
  70          - Fortran 77 and later
  71        * - ``DATAN(X)``
  72          - ``REAL(8) X``
  73          - ``REAL(8)``
  74          - Fortran 77 and later
  75
  76   See also:
  77     Inverse function:
  78     :ref:`TAN`
  79     Degrees function:
  80     :ref:`ATAND`