NAG FL Interface
f06cdf (zcsgs)

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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 <nag.h>
void  f06cdf_ (const Complex *t, Complex *c, double *s)
The routine may be called by the names f06cdf or nagf_blas_zcsgs.

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=sign(Re(t))|t| t1+|t|2 ,  s=ct.  
If |t|<ε, where ε is the machine precision, the routine sets:
c=sign(Re(t))|t|t,  s=sign(Re(t))|t|.  

4 References


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


7 Accuracy

Not applicable.

8 Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.
f06cdf is not threaded in any implementation.

9 Further Comments


10 Example