(libc.info.gz) Inverse Trig Functions

(libc.info.gz) Exponents and Logarithms
 
 19.3 Inverse Trigonometric Functions
 ====================================
 
 These are the usual arc sine, arc cosine and arc tangent functions,
 which are the inverses of the sine, cosine and tangent functions
 respectively.
 
  -- Function: double asin (double X)
  -- Function: float asinf (float X)
  -- Function: long double asinl (long double X)
      Preliminary: | MT-Safe | AS-Safe | AC-Safe |  POSIX Safety
      Concepts.
 
      These functions compute the arc sine of X--that is, the value whose
      sine is X.  The value is in units of radians.  Mathematically,
      there are infinitely many such values; the one actually returned is
      the one between '-pi/2' and 'pi/2' (inclusive).
 
      The arc sine function is defined mathematically only over the
      domain '-1' to '1'.  If X is outside the domain, 'asin' signals a
      domain error.
 
  -- Function: double acos (double X)
  -- Function: float acosf (float X)
  -- Function: long double acosl (long double X)
      Preliminary: | MT-Safe | AS-Safe | AC-Safe |  POSIX Safety
      Concepts.
 
      These functions compute the arc cosine of X--that is, the value
      whose cosine is X.  The value is in units of radians.
      Mathematically, there are infinitely many such values; the one
      actually returned is the one between '0' and 'pi' (inclusive).
 
      The arc cosine function is defined mathematically only over the
      domain '-1' to '1'.  If X is outside the domain, 'acos' signals a
      domain error.
 
  -- Function: double atan (double X)
  -- Function: float atanf (float X)
  -- Function: long double atanl (long double X)
      Preliminary: | MT-Safe | AS-Safe | AC-Safe |  POSIX Safety
      Concepts.
 
      These functions compute the arc tangent of X--that is, the value
      whose tangent is X.  The value is in units of radians.
      Mathematically, there are infinitely many such values; the one
      actually returned is the one between '-pi/2' and 'pi/2'
      (inclusive).
 
  -- Function: double atan2 (double Y, double X)
  -- Function: float atan2f (float Y, float X)
  -- Function: long double atan2l (long double Y, long double X)
      Preliminary: | MT-Safe | AS-Safe | AC-Safe |  POSIX Safety
      Concepts.
 
      This function computes the arc tangent of Y/X, but the signs of
      both arguments are used to determine the quadrant of the result,
      and X is permitted to be zero.  The return value is given in
      radians and is in the range '-pi' to 'pi', inclusive.
 
      If X and Y are coordinates of a point in the plane, 'atan2' returns
      the signed angle between the line from the origin to that point and
      the x-axis.  Thus, 'atan2' is useful for converting Cartesian
      coordinates to polar coordinates.  (To compute the radial
      coordinate, use 'hypot'; see  Exponents and Logarithms.)
 
      If both X and Y are zero, 'atan2' returns zero.
 
    ISO C99 defines complex versions of the inverse trig functions.
 
  -- Function: complex double casin (complex double Z)
  -- Function: complex float casinf (complex float Z)
  -- Function: complex long double casinl (complex long double Z)
      Preliminary: | MT-Safe | AS-Safe | AC-Safe |  POSIX Safety
      Concepts.
 
      These functions compute the complex arc sine of Z--that is, the
      value whose sine is Z.  The value returned is in radians.
 
      Unlike the real-valued functions, 'casin' is defined for all values
      of Z.
 
  -- Function: complex double cacos (complex double Z)
  -- Function: complex float cacosf (complex float Z)
  -- Function: complex long double cacosl (complex long double Z)
      Preliminary: | MT-Safe | AS-Safe | AC-Safe |  POSIX Safety
      Concepts.
 
      These functions compute the complex arc cosine of Z--that is, the
      value whose cosine is Z.  The value returned is in radians.
 
      Unlike the real-valued functions, 'cacos' is defined for all values
      of Z.
 
  -- Function: complex double catan (complex double Z)
  -- Function: complex float catanf (complex float Z)
  -- Function: complex long double catanl (complex long double Z)
      Preliminary: | MT-Safe | AS-Safe | AC-Safe |  POSIX Safety
      Concepts.
 
      These functions compute the complex arc tangent of Z--that is, the
      value whose tangent is Z.  The value is in units of radians.
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