ATAN2(Y, X)

Purpose

Arctangent (inverse tangent) function. The result is the principal value of the nonzero complex number (X, Y) formed by the real arguments Y and X.

Class

Elemental function

Argument Type and Attributes

Y
must be of type real.

X
must be of the same type and kind type parameter as Y. If Y has the value zero, X must not have the value zero.

Result Type and Attributes

Same as X.

Result Value

Examples

ATAN2 (1.5574077, 1.0) has the value 1.0.

Given that:

Y = |  1   1 |        X = | -1  1 |
    | -1  -1 |            | -1  1 |

the value of ATAN2(Y,X) is approximately:

ATAN2 (Y, X) = |  3PI/4   PI/4 |
               | -3PI/4  -PI/4 |


Specific Name Argument Type Result Type Pass As Arg?
ATAN2 default real default real yes
DATAN2 double precision real double precision real yes
QATAN2 (1) REAL(16) REAL(16) yes

Notes:

  1. IBM Extension.

IBM Copyright 2003