LAEV2 - 5.2 English - 68552

LAEV2 computes the eigenvalues and eigenvectors of a 2-by-2 symmetric/Hermitian matrix.

Purpose:

   LAEV2 computes the eigendecomposition of a 2-by-2 symmetric matrix
      [  A   B  ]
      [  B   C  ].
   On   return, RT1 is the eigenvalue of larger absolute value, RT2 is the
   eigenvalue of smaller absolute value, and (CS1,SN1) is the unit right
   eigenvector for RT1, giving the decomposition

      [ CS1  SN1 ] [  A   B  ] [ CS1 -SN1 ]  =  [ RT1  0  ]
      [-SN1  CS1 ] [  B   C  ] [ SN1  CS1 ]     [  0  RT2 ].

Parameters:

• A – [in]

  A is REAL

  The (1,1) element of the 2-by-2 matrix.

• B – [in]

  B is REAL

  The (1,2) element and the conjugate of the (2,1) element of the 2-by-2 matrix.

• C – [in]

  C is REAL

  The (2,2) element of the 2-by-2 matrix.

• RT1 – [out]

  RT1 is REAL

  The eigenvalue of larger absolute value.

• RT2 – [out]

  RT2 is REAL

  The eigenvalue of smaller absolute value.

• CS1 – [out] CS1 is REAL

• SN1 – [out]

  SN1 is REAL

  The vector (CS1, SN1) is a unit right eigenvector for RT1.