NAG Library Routine Document

F06BCF

+− Contents

1 Purpose

9 Example

F06BCF reconstructs the parameters

c

and

s

of a real plane rotation from the tangent of that rotation.

SUBROUTINE F06BCF (

T, C, S)

REAL (KIND=nag_wp)

T, C, S

F06BCF reconstructs the parameters

c

and

s

of a real plane rotation from the value of the tangent

t

, as returned by F06BAF:

c = \frac{1}{\sqrt{1 + t^{2}}}, s = c t,

so that

c \geq 0

and

s

has the same sign as

t

|t| < \sqrt{ε}

, where

ε

is the machine precision, the routine sets

c = 1

and

s = t

; if

|t| > 1 / \sqrt{ε}

, the routine sets

c = \frac{1}{|t|}

and

s = sign t

None.

1: T – REAL (KIND=nag_wp)Input: On entry: the value $t$ , the tangent of the rotation.
2: C – REAL (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.