DLARTG (3lapack)

generate a plane rotation so that [ CS SN ]

SYNOPSIS

  SUBROUTINE DLARTG( F, G, CS, SN, 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.