Provided by: liblapack-doc_3.3.1-1_all

#### NAME

```       LAPACK-3  -  computes  2-by-2  orthogonal matrices U, V and Q, such that if ( UPPER ) then
U**T *A*Q = U**T *( A1 A2 )*Q = ( x 0 )  ( 0 A3 ) ( x x ) and  V**T*B*Q = V**T  *(  B1  B2
)*Q  = ( x 0 )  ( 0 B3 ) ( x x )  or if ( .NOT.UPPER ) then   U**T *A*Q = U**T *( A1 0 )*Q
= ( x x )  ( A2 A3 ) ( 0 x ) and  V**T*B*Q = V**T*( 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**T 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 triangular.
= .FALSE.: the input matrices A and B are lower triangular.

A1      (input) REAL
A2      (input) REAL
A3      (input) REAL
On entry, A1, A2 and A3 are elements 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 elements 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.

LAPACK auxiliary routine (version 3.3.1)   April 2011                            SLAGS2(3lapack)
```