8.18 ATAN2 — Arctangent function

Description:

ATAN2(Y,X) computes the arctangent of the complex number X + i Y.

Option:

f95, gnu

Class:

elemental function

Syntax:

X = ATAN2(Y,X)

Arguments:

Y	The type shall be REAL(*).
X	The type and kind type parameter shall be the same as Y. If Y is zero, then X must be nonzero.

Return value:

The return value has the same type and kind type parameter as Y. It is the principle value of the complex number X + i Y. If X is nonzero, then it lies in the range -\pi \le \arccos (x) \leq \pi. The sign is positive if Y is positive. If Y is zero, then the return value is zero if X is positive and \pi if X is negative. Finally, if X is zero, then the magnitude of the result is \pi/2.

Example:

          program test_atan2
            real(4) :: x = 1.e0_4, y = 0.5e0_4
            x = atan2(y,x)
          end program test_atan2
     

Specific names:

Name	Argument	Return type	Option
DATAN2(X)	REAL(8) X	REAL(8)	f95, gnu