f06bcf (PDF version)
F06 (blas) Chapter Contents
F06 (blas) Chapter Introduction
NAG Library Manual
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NAG Library Routine Document
f06bcf (dcsg)
▸
▿
Contents
1
Purpose
2
Specification
3
Description
4
References
5
Arguments
6
Error Indicators and Warnings
7
Accuracy
8
Parallelism and Performance
9
Further Comments
10
Example
1
Purpose
f06bcf
reconstructs the parameters
c
and
s
of a real plane rotation from the tangent of that rotation.
2
Specification
Fortran Interface
Subroutine f06bcf (
t
,
c
,
s
)
Real (Kind=nag_wp), Intent (In)
::
t
Real (Kind=nag_wp), Intent (Out)
::
c
,
s
C Header Interface
#include nagmk26.h
void
f06bcf_ (
const double *
t
,
double *
c
,
double *
s
)
3
Description
f06bcf
reconstructs the parameters
c
and
s
of a real plane rotation from the value of the tangent
t
, as returned by
f06baf
:
c
=
1
1
+
t
2
,
s
=
c
t
,
so that
c
≥
0
and
s
has the same sign as
t
.
If
t
<
ε
, where
ε
is the
machine precision
, the routine sets
c
=
1
and
s
=
t
; if
t
>
1
/
ε
, the routine sets
c
=
1
t
and
s
=
sign
t
.
4
References
None.
5
Arguments
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.
6
Error Indicators and Warnings
None.
7
Accuracy
Not applicable.
8
Parallelism and Performance
f06bcf
is not threaded in any implementation.
9
Further Comments
None.
10
Example
None.
f06bcf (PDF version)
F06 (blas) Chapter Contents
F06 (blas) Chapter Introduction
NAG Library Manual
© The Numerical Algorithms Group Ltd, Oxford, UK. 2017