On 21 zář, 12:08, "[email protected]" <[email protected]> wrote:
> Error in desolve - it starts different process for Maxima. solved
> inhttp://trac.sagemath.org/sage_trac/ticket/9835(needs_review).
I tested examples which worked in Maxima but did not work in Sage.
With this patch we have
ma...@um-bc107:/opt/sage$ ./sage
----------------------------------------------------------------------
| Sage Version 4.5.3, Release Date: 2010-09-04 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
sage: assume(x>0)
sage: y=function('y',x)
sage: assume(y>0)
sage: desolve(x*diff(y,x)-x*sqrt(y^2+x^2)-y,y,contrib_ode=True)
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/opt/sage-4.5.3-Debian_Lenny_64-x86_64-Linux/<ipython console> in
<module>()
/opt/sage-4.5.3-Debian_Lenny_64-x86_64-Linux/local/lib/python2.6/site-
packages/sage/calculus/desolvers.pyc in desolve(de, dvar, ics, ivar,
show_method, contrib_ode)
423 # we produce string like this
424 # (TEMP:contrib_ode(x*('diff(y,x,1))^2-(x*y
+1)*'diff(y,x,1)+y,y,x), if TEMP=false then TEMP else
substitute(y=y(x),TEMP))
--> 425 soln = P(cmd)
426 if str(soln).strip() == 'false':
427 raise NotImplementedError, "Maxima was unable
to solve this ODE."
/opt/sage-4.5.3-Debian_Lenny_64-x86_64-Linux/local/lib/python2.6/site-
packages/sage/interfaces/expect.pyc in __call__(self, x, name)
1030
1031 if isinstance(x, basestring):
-> 1032 return cls(self, x, name=name)
1033 try:
1034 return self._coerce_from_special_method(x)
/opt/sage-4.5.3-Debian_Lenny_64-x86_64-Linux/local/lib/python2.6/site-
packages/sage/interfaces/expect.pyc in __init__(self, parent, value,
is_name, name)
1449 except (TypeError, KeyboardInterrupt,
RuntimeError, ValueError), x:
1450 self._session_number = -1
-> 1451 raise TypeError, x
1452 self._session_number = parent._session_number
1453
TypeError: Computation failed since Maxima requested additional
constraints (try the command 'assume(y>0)' before integral or limit
evaluation, for example):
Is y zero or nonzero?
On the other hand, declaring y as variable first, assuming y>0 and
declaring y as a function helps
ma...@um-bc107:/opt/sage$ ./sage
----------------------------------------------------------------------
| Sage Version 4.5.3, Release Date: 2010-09-04 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
sage: assume(x>0)
sage: y=var('y')
sage: assume(y>0)
sage: y=function('y',x)
sage: desolve(x*diff(y,x)-x*sqrt(y^2+x^2)-y,y,contrib_ode=True)
[x - arcsinh(y(x)/x) == c]
Any explanation for this? Is it a bug? In assume facility?
Thanks
Robert
>
> Robert
>
> On 21 zář, 03:26, Oscar Gerardo Lazo Arjona
>
> <[email protected]> wrote:
> > Hello!
>
> > I'm trying to solve this ODE:
>
> > var('t alpha beta n')
> > x=function('x',t)
> > eq=diff(x,t)^2==alpha-beta abs(x)^n
> > assume(n,'integer')
> > desolve(eq,x,ivar=t,contrib_ode=True)
>
> > but I get:
>
> > Traceback (click to the left of this block for traceback)
> > ...
> > Is n an integer?
>
> > but I've already told sage that n is an integer.
>
> > I'm using sage 4.5.2
>
> > thank you
>
> > Oscar
>
>
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