8.21 ATAN — Arctangent function

Description:

ATAN(X) computes the arctangent of X.

Standard:

Fortran 77 and later, for a complex argument and for two arguments Fortran 2008 or later

Class:

Elemental function

Syntax:

RESULT = ATAN(X)

RESULT = ATAN(Y, X)

Arguments:

X	The type shall be REAL or COMPLEX; if Y is present, X shall be REAL.
Y shall be of the same type and kind as X.

Return value:

The return value is of the same type and kind as X. If Y is present, the result is identical to ATAN2(Y,X). Otherwise, it the arcus tangent of X, where the real part of the result is in radians and lies in the range -\pi/2 \leq \Re \atan(x) \leq \pi/2.

Example:

program test_atan
  real(8) :: x = 2.866_8
  x = atan(x)
end program test_atan

Specific names:

Name	Argument	Return type	Standard
ATAN(X)	REAL(4) X	REAL(4)	Fortran 77 and later
DATAN(X)	REAL(8) X	REAL(8)	Fortran 77 and later

See also:

Inverse function: TAN