atan

Date:: 10-12-2011

NAME

ATAN, DATAN, ATAND, DATAND - Compute arctangent (inverse tangent) for single argument

SYNOPSIS

ATAN ([X=]x)
DATAN ([X=]x)
ATAND ([X=]x) (Deferred implementation)
DATAND ([X=]x) (Deferred implementation)

STANDARDS

Fortran

Fortran extensions: ATAND DATAND

DESCRIPTION

ATAN and DATAN return the arctangent in radians. ATAND and DATAND return the arctangent in degrees.

ATAN and ATAND are generic function names; the others are specifics. These are elemental intrinsic functions that accept the following argument:

x: Must be type real. The type and kind type of x is identical to the type and kind type of the return value. See the RETURN VALUES section for information on input data types and return values.

These functions evaluate y = arctan(x).

The result range for ATAN and DATAN is -pi/2 <= ATAN(x) <= pi/2.

The result range for ATAND and DATAND is -90 <= result <= 90.

There are vector versions of the ATAN and DATAN intrinsics.

NOTES

The ATAN and DATAN intrinsic function names can be passed as arguments; the others cannot.

The following is returned if NaN or infinity is passed to the CATAN function:

ATAN(NaN) yields NaN.
ATAN(infinity) yields pi/2.
ATAN(-infinity) yields -pi/2.

Note: The atan() function has a Linux-equivalent name. Use the man -aname option to show all manual pages matching name within the MANPATH search path. Manual pages are displayed in the order found.

RETURN VALUES

ATAN and ATAND return the real arctangent of their real arguments.

DATAN and DATAND return the double-precision arctangent of their double-precision arguments.