#
Fortran Wiki

atan

## 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 $-\pi / 2 \leq \mathop{Re}{\atan(x)} \leq \pi / 2$.

## Example

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

## See also

atan2, tan

Revised on April 3, 2016 22:28:26
by

Jason Blevins
(173.88.47.127)
(955 characters / 0.0 pages)