NAG Library Routine Document

f06cdf (zcsgs)

1
Purpose

f06cdf reconstructs the parameters c (complex) and s (real) of a complex plane rotation from the tangent of that rotation.

2
Specification

Fortran Interface
Subroutine f06cdf ( t, c, s)
Real (Kind=nag_wp), Intent (Out):: s
Complex (Kind=nag_wp), Intent (In):: t
Complex (Kind=nag_wp), Intent (Out):: c
C Header Interface
#include <nagmk26.h>
void  f06cdf_ (const Complex *t, Complex *c, double *s)

3
Description

f06cdf reconstructs the parameters c (complex) and s (real) of a complex plane rotation, from the value of the tangent t, as returned by f06cbf:
c=signRett t1+t2 ,  s=ct.  
If t<ε, where ε is the machine precision, the routine sets:
c=signRettt,  s=signRett.  

4
References

None.

5
Arguments

1:     t – Complex (Kind=nag_wp)Input
On entry: the value t, the tangent of the rotation.
2:     c – Complex (Kind=nag_wp)Output
On exit: the value c, the cosine of the rotation.
3:     s – Real (Kind=nag_wp)Output
On exit: the value s, the sine of the rotation.

6
Error Indicators and Warnings

None.

7
Accuracy

Not applicable.

8
Parallelism and Performance

f06cdf is not threaded in any implementation.

9
Further Comments

None.

10
Example

None.