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)