NAG Library Routine Document

F06CDF

+− Contents

1 Purpose

9 Example

F06CDF reconstructs the parameters

c

(complex) and

s

(real) of a complex plane rotation from the tangent of that rotation.

SUBROUTINE F06CDF (

T, C, S)

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

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 = \frac{sign (Re (t)) |t|}{t \sqrt{1 + {|t|}^{2}}}, s = c t .

|t| < \sqrt{ε}

, where

ε

is the machine precision, the routine sets:

c = \frac{sign (Re (t)) |t|}{t}, s = sign (Re (t)) |t| .

None.

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.