..
  Copyright 1988-2021 Free Software Foundation, Inc.
  This is part of the GCC manual.
  For copying conditions, see the GPL license file

.. _asin:

ASIN --- Arcsine function 
**************************

.. index:: ASIN

.. index:: DASIN

.. index:: trigonometric function, sine, inverse

.. index:: sine, inverse

.. function:: ASIN(X)

  ``ASIN(X)`` computes the arcsine of its :samp:`{X}` (inverse of ``SIN(X)`` ).

  :param X:
    The type shall be either ``REAL`` and a magnitude that is
    less than or equal to one - or be ``COMPLEX``.

  :return:
    The return value is of the same type and kind as :samp:`{X}`.
    The real part of the result is in radians and lies in the range
    -\pi/2 \leq \Re \asin(x) \leq \pi/2.

  :samp:`{Standard}:`
    Fortran 77 and later, for a complex argument Fortran 2008 or later

  :samp:`{Class}:`
    Elemental function

  :samp:`{Syntax}:`

  .. code-block:: fortran

    RESULT = ASIN(X)

  :samp:`{Example}:`

    .. code-block:: fortran

      program test_asin
        real(8) :: x = 0.866_8
        x = asin(x)
      end program test_asin

  :samp:`{Specific names}:`
    ============  =============  ===========  ====================
    Name          Argument       Return type  Standard
    ============  =============  ===========  ====================
    ``ASIN(X)``   ``REAL(4) X``  ``REAL(4)``  Fortran 77 and later
    ``DASIN(X)``  ``REAL(8) X``  ``REAL(8)``  Fortran 77 and later
    ============  =============  ===========  ====================

  :samp:`{See also}:`
    Inverse function: 
    SIN 
    Degrees function: 
    ASIND