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D.8.4.12 triang_solve

Procedure from library solve.lib (see solve_lib).

Usage:
triang_solve(l,p [,d] ); l=list, p,d=integers
l is a list of finitely many triangular systems, such that the union of their varieties equals the variety of the initial ideal.
p>0: gives precision of complex numbers in digits,
d>0: gives precision (1<d<p) for near-zero-determination,
(default: d=1/2*p).

Assume:
the ground field has char 0;
l was computed using the algorithm of Lazard or the algorithm of Moeller (see triang.lib).

Return:
ring R with the same number of variables, but with complex coefficients (and precision p). R comes with a list rlist of numbers, in which the complex roots of l are stored.

Example:
 
LIB "solve.lib";
ring r = 0,(x,y),lp;
// compute the intersection points of two curves
ideal s=  x2 + y2 - 10, x2 + xy + 2y2 - 16;
def R=triang_solve(triangLfak(stdfglm(s)),10);
==> 
==> // 'triang_solve' created a ring, in which a list rlist of numbers (the
==> // complex solutions) is stored.
==> // To access the list of complex solutions, type (if the name R was assig\
   ned
==> // to the return value):
==>         setring R; rlist; 
setring R; rlist;
==> [1]:
==>    [1]:
==> -1
==>    [2]:
==> 3
==> [2]:
==>    [1]:
==> 1
==>    [2]:
==> -3
==> [3]:
==>    [1]:
==> -2.828427125
==>    [2]:
==> -1.414213562
==> [4]:
==>    [1]:
==> 2.828427125
==>    [2]:
==> 1.414213562