F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

# NAG Library Routine DocumentF06CDF

Note:  before using this routine, please read the Users' Note for your implementation to check the interpretation of bold italicised terms and other implementation-dependent details.

## 1  Purpose

F06CDF reconstructs the parameters $c$ (complex) and $s$ (real) of a complex plane rotation from the tangent of that rotation.

## 2  Specification

 SUBROUTINE F06CDF ( T, C, S)
 REAL (KIND=nag_wp) S COMPLEX (KIND=nag_wp) T, C

## 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:
 $c=signRett t⁢1+t2 , s=ct.$
If $\left|t\right|<\sqrt{\epsilon }$, where $\epsilon$ is the machine precision, the routine sets:
 $c=signRettt, s=signRett.$

None.

## 5  Parameters

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.

None.

Not applicable.