Hi Yotam,
On Sat, Nov 28, 2009 at 5:03 AM, Yotam Avital <yota...@gmail.com> wrote:
<SNIP>
> As I far as I can understand, solution_dict tells sage that I want the
> output to be in dictionary form(that is, {x:1, y:8 ...})
Yes, you're right.
> I also know that the .n(30) tell sage I want the answer to have 30 digits
> accuracy.
Not quite. The method .n(30) tells Sage that you want an approximation
with 30 bits of precision. The default is to use 53 bits of precision.
This method has two keywords: "prec" for specifying the number of bits
of precision; and "digits" for specifying the number of digits. For
example, consider the following Sage session:
{{{
[mv...@sage ~]$ sage
----------------------------------------------------------------------
| Sage Version 4.2.1, Release Date: 2009-11-14 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
sage: var('x, y, p, q');
sage: eq1 = p + q == 9
sage: eq2 = q*y + p*x == -6
sage: eq3 = q*y^2 + p*x^2 == 24
sage: solns = solve([eq1, eq2, eq3, p==1], p, q, x, y, solution_dict=True)
sage: sol = solns[0][p]
sage: # approximate sol with 30 bits of precision
sage: sol.n(30)
1.0000000
sage: sol.n(prec=30)
1.0000000
sage: # approximate sol with 30 digits of precision
sage: sol.n(digits=30)
1.00000000000000000000000000000
}}}
You can find out more about the method .n() by issuing "sol.n?" at the
command line.
> I can't understand though the logic of the last command. Can any
> of you explain it to me?
You were asking for an approximation with 30 bits of precision. If you
want an approximation with 30 digits of precision, use the key word
"digits" of the method .n().
--
Regards
Minh Van Nguyen
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