[sage-support] Re: Integration bug?
On 2018-10-02, kcrisman wrote: > Please do. It's likely something related to > https://trac.sagemath.org/ticket/21440 and > https://trac.sagemath.org/wiki/symbolics#Integrationtickets where you can > browse to your heart's content :-) For some reason the wrong branch seems > to get chosen by Maxima at times. OK, I'll add the example at #21440. Best regards, Simon -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
[sage-support] Re: Integration bug?
On Monday, October 1, 2018 at 4:55:14 PM UTC-4, Simon King wrote: > > Hi! > > I get the following with sage-8.4.beta5: > sage: f(x) = cos(pi*x) > sage: (f(x)*exp(-I*pi*x)).integral(x)(x=1/2) - > (f(x)*exp(-I*pi*x)).integral(x)(x=-1/2) > 1/2 > sage: (f(x)*exp(-I*pi*x)).integral(x,-1/2,1/2) > 1 > > The previous two expressions are not equal, but I think they should be > equal. Is it a stupid mistake of mine (but then, Wolfram alpha does the > same stupid mistake), is it a known bug, or a new bug (in that case I > should create some ticket, that would probably be my first on > calculus...)? > Please do. It's likely something related to https://trac.sagemath.org/ticket/21440 and https://trac.sagemath.org/wiki/symbolics#Integrationtickets where you can browse to your heart's content :-) For some reason the wrong branch seems to get chosen by Maxima at times. For what it's worth: sage: (f(x)*exp(-I*pi*x)).integral(x,-1/2,1/2,algorithm='sympy') 1/2 -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
[sage-support] Re: Integration bug?
> integral(sqrt(1+cos(x)^2),x,0,pi) > > > > 0 > > The bug appears to be tickled by the Maxima package abs_integrate. > Without abs_integrate, integrate(sqrt(1 + cos(x)^2), x, 0, %pi) just > returns a noun expression. > > > Zero is decidedly not correct. The problem is apparently here: > > > > integral(sqrt(1+cos(x)^2),x) > > > > -1/24*sin(3*x) + 1/8*sin(x) > > Hmm, for the indefinite integral I get (with abs_integrate) > > (%i4) integrate(sqrt(1+cos(x)^2),x); > (%o4) ((2*sin(3*x)+6*sin(x))*false-sin(3*x)+3*sin(x))/24 > > See https://trac.sagemath.org/ticket/12731 for lots more examples (also https://trac.sagemath.org/wiki/symbolics#Integrationtickets). A lot of these are reported upstream but since we are using the package I think they are less likely to get attention than core Maxima functionality. (And I haven't been helpful lately on them either, so no aspersions are being cast.) -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
[sage-support] Re: Integration bug?
On 2017-10-26, david.guichard wrote: > integral(sqrt(1+cos(x)^2),x,0,pi) > > 0 The bug appears to be tickled by the Maxima package abs_integrate. Without abs_integrate, integrate(sqrt(1 + cos(x)^2), x, 0, %pi) just returns a noun expression. > Zero is decidedly not correct. The problem is apparently here: > > integral(sqrt(1+cos(x)^2),x) > > -1/24*sin(3*x) + 1/8*sin(x) Hmm, for the indefinite integral I get (with abs_integrate) (%i4) integrate(sqrt(1+cos(x)^2),x); (%o4) ((2*sin(3*x)+6*sin(x))*false-sin(3*x)+3*sin(x))/24 Obviously the presence of 'false' is a bug. If you can make a bug report in the Maxima bug tracker, that would very helpful. https://sourceforge.net/p/maxima/bugs By the way I am working with Maxima 5.40+ (almost 5.41). best, Robert Dodier -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
[sage-support] Re: Integration bug?
On Tuesday, March 27, 2012 4:25:48 PM UTC-4, david.guichard wrote:
>
> I've tried this on my 4.6 sage and on 5.0 beta; the main sagenb.org is
> not returning calculations for me. Both 4.6 and 5.0 have the same error.
> This double integral calculation is correct:
>
> var("r t")
> f=integral(sqrt(1-r^2*cos(t)^2)*r,r,0,1)
> g=integral(f,t)
> g; g(t=pi/4)-g(t=0)
>
> but this one is not:
>
> integral(f,t,0,pi/4)
>
>
I tried this out a bit in Maxima, and it seems that there it's even easier
to get the wrong result. I suspect that sqrt(-cos(t)^2 + 1) might be in a
situation where it's considered sin(t) or something...
in Sage:
sage: integral(f,t)
-1/3*(tan(t)^2 + 2)/sqrt(tan(t)^2 + 1) + 1/3*tan(t)
in Maxima:
(%i10) g
;
(%o10) ((sin(3 t) + sin(t)) sin(4 t) + (cos(3 t) + cos(t)) cos(4 t)
+ 6 sin(2 t) sin(3 t) + (6 cos(2 t) + 1) cos(3 t) + 6 sin(t) sin(2 t)
2
+ 6 cos(t) cos(2 t) + cos(t))/(3 (2 sin (3 t) + 4 sin(t) sin(3 t)
2 2 2tan(t)
+ 2 cos (3 t) + 4 cos(t) cos(3 t) + 2 sin (t) + 2 cos (t))) + --
3
Not sure what's going on with this, but I really suspect there's some
unfortunate simplifications somewhere. I'm sorry I don't have time to look
more into this right now :(
--
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