Language Reference

+-------------------------------IBM Extension--------------------------------+

ATAN2D(Y, X)

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.

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.

Class

Elemental function

Result Type and Attributes

Same as X.

Result Value

• 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°.

Examples

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 |

+----------------------------End of IBM Extension----------------------------+