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# slags2

```
NAME
SLAGS2 - compute 2-by-2 orthogonal matrices U, V and Q, such
that if ( UPPER ) then   U'*A*Q = U'*( A1 A2 )*Q = ( x 0 )
( 0 A3 ) ( x x ) and  V'*B*Q = V'*( B1 B2 )*Q = ( x 0 )  ( 0
B3 ) ( x x )  or if ( .NOT.UPPER ) then   U'*A*Q = U'*( A1 0
)*Q = ( x x )  ( A2 A3 ) ( 0 x ) and  V'*B*Q = V'*( B1 0 )*Q
= ( x x )  ( B2 B3 ) ( 0 x )  The rows of the transformed A
and B are parallel, where   U = ( CSU SNU ), V = ( CSV SNV
), Q = ( CSQ SNQ )  ( -SNU CSU ) ( -SNV CSV ) ( -SNQ CSQ )
Z' denotes the transpose of Z

SYNOPSIS
SUBROUTINE SLAGS2( UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU,
CSV, SNV, CSQ, SNQ )

LOGICAL        UPPER

REAL           A1, A2, A3, B1, B2, B3, CSQ, CSU, CSV,
SNQ, SNU, SNV

PURPOSE
SLAGS2 computes 2-by-2 orthogonal matrices U, V and Q, such
that if ( UPPER ) then

ARGUMENTS
UPPER   (input) LOGICAL
= .TRUE.: the input matrices A and B are upper tri-
angular.
= .FALSE.: the input matrices A and B are lower tri-
angular.

A1      (input) REAL
A2      (input) REAL A3      (input) REAL On entry,
A1, A2 and A3 are entries of the input 2-by-2 upper
(lower) triangular matrix A.

B1      (input) REAL
B2      (input) REAL B3      (input) REAL On entry,
B1, B2 and B3 are entries of the input 2-by-2 upper
(lower) triangular matrix B.

CSU     (output) REAL
SNU     (output) REAL The desired orthogonal matrix
U.

CSV     (output) REAL
SNV     (output) REAL The desired orthogonal matrix
V.

CSQ     (output) REAL

SNQ     (output) REAL The desired orthogonal matrix
Q.
```