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RedHat 9 (Linux i386) - man page for dlae2 (redhat section l)

DLAE2(l)					)					 DLAE2(l)

NAME
       DLAE2 - compute the eigenvalues of a 2-by-2 symmetric matrix [ A B ] [ B C ]

SYNOPSIS
       SUBROUTINE DLAE2( A, B, C, RT1, RT2 )

	   DOUBLE	 PRECISION A, B, C, RT1, RT2

PURPOSE
       DLAE2  computes	the  eigenvalues of a 2-by-2 symmetric matrix [ A B ] [ B C ]. On return,
       RT1 is the eigenvalue of larger absolute value, and RT2 is the eigenvalue of smaller abso-
       lute value.

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

       B       (input) DOUBLE PRECISION
	       The (1,2) and (2,1) elements of the 2-by-2 matrix.

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

       RT1     (output) DOUBLE PRECISION
	       The eigenvalue of larger absolute value.

       RT2     (output) DOUBLE PRECISION
	       The eigenvalue of smaller absolute value.

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  com-
       pute RT2 accurately in all cases.

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

LAPACK version 3.0			   15 June 2000 				 DLAE2(l)


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