`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