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2011-10-17 18:35:40 +0200 answered a question How to startX (show desktop GUI) on VirtualBox / VMWare ?

Thanks a lot.
I have understood the idea.
I installed gnome-desktop but startx command still can't be found.
("find / -name startx" returns no match.)

I appreciate if you could tell me how to start GNOME desktop.

2011-10-14 22:20:19 +0200 asked a question How to startX (show desktop GUI) on VirtualBox / VMWare ?

Hi, experts.

I tried both VirtualBox and VMWare to use Sage 4.7.1 on Windows.
But both of them starts up with CUI (Character User Interface).
Uploaded the screenshot at
- VirtualBox: http://blog-imgs-24.fc2.com/e/u/r/eurekass/vb.jpg
- VMWare: http://blog-imgs-24.fc2.com/e/u/r/eurekass/vmw.jpg

I tried the command "startx", but the error "command not found." returned.

Is there any way to startX (show desktop GUI) like LiveCD version ?

2011-10-14 09:11:25 +0200 asked a question assume() seems not to work for a specific case...

Hi, experts

I tried the following commands:

var('a, b, c')
assume(a>0, b>0, c>0)
solve([a*(b+c)==0, b*(c-a)==0, c*(a+b)==0], a,b,c)

expecting sage to return only (a,b,c) = (k, -k, k).

However, sage returned
(a,b,c) = (k, 0, 0), (0, k, 0), (0, 0, k), (k, -k, k).
though I typed 'assume(a>0, b>0, c>0)'.

Is there any way to invalidate the first 3 answers ?

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2011-10-10 23:29:55 +0200 answered a question How to Rationalize the Denominator of a Fraction ?

Thank you for your reply.
maxima_methods seems to be useful.

I also found another way to set algebraic to true.

sage: maxima('ratsimp(a) algebraic: true')

Though this method seems to send the maxima command as a string to Maxima.

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2011-10-09 03:25:35 +0200 asked a question How to Rationalize the Denominator of a Fraction ?

Hi, experts.

Is there any way to rationalize the denomintor of a fraction ?

For example, I tried

a = 1 / (2 * sqrt(2) + 3)

b = a.simplify_full(); b;
c = a.simplify_factorial(); c;
d = a.simplify_radical(); d;
e = a.simplify_rational(); e;

expecting any of them to return "3 - 2*sqrt(2)" or "-2*sqrt(2) + 3".

However, all of the above commands return 1/(2*sqrt(2) + 3),
whose denominator is not rational.

I know
(1) Sage uses Maxima.
(2) Standalone version of Maxima can rationalize the denominator by typing "ratsimp(a), algebraic: true;".
(3) Sage accepts "maxima.ratsimp(a)", but I don't know how to pass the Maxima option "algebraic: true;" to Sage.

Is there any way to rationalize the denominator with Sage ?

Thanks in advance.
-Tatsuya