NAME

dlartg - generate a plane rotation so that   [ CS SN ]

SYNOPSIS

SUBROUTINE DLARTG(
F, G, CS, SN, R )

void dlartg(double f, double g, double ∗cs,
double ∗sn, double ∗r)

DOUBLE PRECISION CS, F, G, R, SN

PURPOSE

DLARTG generate a plane rotation so that
   [ -SN  CS  ]     [ G ]     [ 0 ]
 
This is a slower, more accurate version of the BLAS1 routine DROTG, with the following other differences:
   F and G are unchanged on return.
   If G=0, then CS=1 and SN=0.
   If F=0 and (G .ne. 0), then CS=0 and SN=1 without doing any
      floating point operations (saves work in DBDSQR when
      there are zeros on the diagonal).
 
If F exceeds G in magnitude, CS will be positive.
 

ARGUMENTS

F       (input) DOUBLE PRECISION
The first component of vector to be rotated.

G       (input) DOUBLE PRECISION
The second component of vector to be rotated.

CS      (output) DOUBLE PRECISION
The cosine of the rotation.

SN      (output) DOUBLE PRECISION
The sine of the rotation.

R       (output) DOUBLE PRECISION
The nonzero component of the rotated vector.

Sun, Inc.  —  Last change: 20 Sep 1996