Fri Mar 15 14:30:11 EDT 2013
See also . I'm looking for a simpler, a-symmetric approach where
only one of the coefficients is updated, e.g. c. Solving for f(c) = 0 in
f(c) = (c^2 + s^2) - 1
the N-R update is:
u(c) = c - f(c) / f'(c)
= c - (c^2 + s^2 - 1) / 2c
= 1/2 (c + (1-s^2)/c)
This is probably much more precise than the other method, but it uses
a division operator. Also, it's symmetric in c and s, so if c->0 we
can switch to the s form.
The direct form is probably better.