ATAN

This function extends FORTRAN’s generic function ATAN to evaluate the complex arc tangent.

Function Return Value

ATAN — Complex function value in units of radians with the real part in the first or fourth quadrant. (Output)

Required Arguments

Z — Complex argument for which the arc tangent is desired. (Input)

FORTRAN 90 Interface

Generic: ATAN (Z)

Specific: The specific interface names are CATAN and ZATAN.

FORTRAN 77 Interface

Complex: CATAN (Z)

Double complex:The double complex function name is ZATAN.

Description

The argument z must not be exactly ±i, because tan‑1 z is undefined there. In addition, z must not be so close to ±i that substantial significance is lost.

Comments

Informational error

 

Type	Code	Description
3	2	Result of ATAN(Z) is accurate to less than one-half precision because ∣Z2∣ is too close to ‑1.0.

Example

In this example, tan‑1(0.01 + 0.01i) is computed and printed.

 

USE ATAN_INT

USE UMACH_INT

 

IMPLICIT NONE

! Declare variables

INTEGER NOUT

COMPLEX VALUE, Z

! Compute

Z = (0.01, 0.01)

VALUE = ATAN(Z)

! Print the results

CALL UMACH (2, NOUT)

WRITE (NOUT,99999) Z, VALUE

99999 FORMAT (' ATAN((', F6.3, ',', F6.3, ')) = (', &

F6.3, ',', F6.3, ')')

END

Output

 

ATAN(( 0.010, 0.010)) = ( 0.010, 0.010)