ATAN2D(Y, X) (IBM extension)

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.

Elemental function

Y: An INTENT(IN) REAL
X: An INTENT(IN) argument of the same type and kind type parameter as Y. If Y has the value zero, X must not have the value zero.

Same as X.

It is expressed in degrees and has a value equal to the principal value of the argument of the complex number (X, Y).
It is in the range -180° < ATAN2D(Y,X) ≤ 180°.
If X≠0, the result approximates arctan(Y/X).
If Y>0, the result is positive.
If Y<0, the result is negative.
If Y=0 and X>0, the result is zero.
If Y=0 and X<0, the result is 180°.
If X=0, the absolute value of the result is 90°.

ATAN2D (1.5574077, 1.0) has the value 57.295780181° (approximately).

Given that:

Y = |  1.0   1.0 |   X = | -1.0   1.0 |
    | -1.0  -1.0 |       | -1.0   1.0 |

then the value of ATAN2D(Y,X) is:

ATAN2D(Y,X) =  |  135.0000000°   45.00000000° |
               | -135.0000000°  -45.00000000° |

Specific Name	Argument Type	Result Type	Pass As Arg?
ATAN2D	default real	default real	yes
DATAN2D	double precision real	double precision real	yes
QATAN2D	REAL(16)	REAL(16)	yes