Refine polynomial roots using Newton–Raphson¶
This is an implementation of the Newton–Raphson algorithm to approximate roots of complex polynomials. The implementation is based on interval arithmetic
AUTHORS:
 Carl Witty (20071118): initial version

sage.rings.polynomial.refine_root.
refine_root
(ip, ipd, irt, fld)¶ We are given a polynomial and its derivative (with complex interval coefficients), an estimated root, and a complex interval field to use in computations. We use interval arithmetic to refine the root and prove that we have in fact isolated a unique root.
If we succeed, we return the isolated root; if we fail, we return None.
EXAMPLES:
sage: from sage.rings.polynomial.refine_root import refine_root sage: x = polygen(ZZ) sage: p = x^9  1 sage: ip = CIF['x'](p); ip x^9  1 sage: ipd = CIF['x'](p.derivative()); ipd 9*x^8 sage: irt = CIF(CC(cos(2*pi/9), sin(2*pi/9))); irt 0.76604444311897802? + 0.64278760968653926?*I sage: ip(irt) 0.?e14 + 0.?e14*I sage: ipd(irt) 6.89439998807080?  5.78508848717885?*I sage: refine_root(ip, ipd, irt, CIF) 0.766044443118978? + 0.642787609686540?*I