Intel® Fortran Compiler Classic and Intel® Fortran Compiler Developer Guide and Reference
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ATAN2
Elemental Intrinsic Function (Generic): Produces an arctangent (inverse tangent). The result is the principal value of the argument of the nonzero complex number (x, y).
result = ATAN2 (y,x)
| y | (Input) Must be of type real. | 
| x | (Input) Must have the same type and kind parameters as y. If y has the value zero, x cannot have the value zero. | 
The result type and kind are the same as x and are expressed in radians. The value lies in the range -pi <= ATAN2 (y, x) <= pi.
If x is not zero, the result is approximately equal to the value of arctan (y/ x).
If y > zero, the result is positive.
If y < zero, the result is negative.
If y is zero and x > zero, the result is y (so for x>0, ATAN2 ((+0.0), x) is +0.0 and ATAN2 ((-0.0), x) is -0.0).
If y is a positive real zero and x < zero, the result is pi.
If y is a negative real zero and x < zero, the result is -pi.
If x is a positive real zero, the result is pi/2.
If y is a negative real zero, the result is -pi/2.
| Specific Name | Argument Type | Result Type | 
|---|---|---|
| ATAN2 | REAL(4) | REAL(4) | 
| DATAN2 | REAL(8) | REAL(8) | 
| QATAN2 | REAL(16) | REAL(16) | 
ATAN2 (2.679676, 1.0) has the value 1.213623.
If Y is an array that has the value
[ 1 1 ] [ -1 -1 ]
and X is an array that has the value
[ -1 1 ] [ -1 1 ],
then ATAN2 (Y, X) is
