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dlaev2.f(3)				      LAPACK				      dlaev2.f(3)

NAME
       dlaev2.f -

SYNOPSIS
   Functions/Subroutines
       subroutine dlaev2 (A, B, C, RT1, RT2, CS1, SN1)
	   DLAEV2 computes the eigenvalues and eigenvectors of a 2-by-2 symmetric/Hermitian
	   matrix.

Function/Subroutine Documentation
   subroutine dlaev2 (double precisionA, double precisionB, double precisionC, double
       precisionRT1, double precisionRT2, double precisionCS1, double precisionSN1)
       DLAEV2 computes the eigenvalues and eigenvectors of a 2-by-2 symmetric/Hermitian matrix.

       Purpose:

	    DLAEV2 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

		     A is DOUBLE PRECISION
		     The (1,1) element of the 2-by-2 matrix.

	   B

		     B is DOUBLE PRECISION
		     The (1,2) element and the conjugate of the (2,1) element of
		     the 2-by-2 matrix.

	   C

		     C is DOUBLE PRECISION
		     The (2,2) element of the 2-by-2 matrix.

	   RT1

		     RT1 is DOUBLE PRECISION
		     The eigenvalue of larger absolute value.

	   RT2

		     RT2 is DOUBLE PRECISION
		     The eigenvalue of smaller absolute value.

	   CS1

		     CS1 is DOUBLE PRECISION

	   SN1

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

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   September 2012

       Further Details:

	     RT1 is accurate to a few ulps barring over/underflow.

	     RT2 may be inaccurate if there is massive cancellation in the
	     determinant A*C-B*B; higher precision or correctly rounded or
	     correctly truncated arithmetic would be needed to compute RT2
	     accurately in all cases.

	     CS1 and SN1 are accurate to a few ulps barring over/underflow.

	     Overflow is possible only if RT1 is within a factor of 5 of overflow.
	     Underflow is harmless if the input data is 0 or exceeds
		underflow_threshold / macheps.

       Definition at line 121 of file dlaev2.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2				 Tue Sep 25 2012			      dlaev2.f(3)
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