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Simplification fails

asked 2020-04-27 04:18:46 -0500

Cyrille gravatar image

updated 2020-04-27 07:39:54 -0500

1) I have tried nearly all simplification methods, expansion, factorization, collect... on the following code for Ra1

var("x,a")
Ra1 = -diff(x^a, x,2)/diff(x^a, x)
show(Ra1)

but the self-evident simplification doesn't work. I wonder why. I also have tried to add assumption even I do not see why since it's only algebra

2) Is there a way to ask SM to factor on a variable ?

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answered 2020-04-27 08:19:32 -0500

slelievre gravatar image

updated 2020-04-27 08:47:09 -0500

The first question is about simplyfing a symbolic expression.

The method simplify_log seems to do the trick.

sage: x, a = SR.var('x a')
sage: Ra1 = -diff(x^a, x,2)/diff(x^a, x)
sage: Ra1
-(a - 1)*x^(a - 2)/x^(a - 1)
sage: Ra1.simplify_log()
-(a - 1)/x

I suppose the second question is about SageManifolds, but I'm not sure exactly what the question is.

Maybe this can help:

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when I apply simplify_log() I have the following error

ECL says: Error executing code in Maxima:

Cyrille gravatar imageCyrille ( 2020-04-27 09:46:27 -0500 )edit

@Cyrille I have no error, maybe you forget to change the code from var to SR.var

Masacroso gravatar imageMasacroso ( 2020-04-27 14:25:29 -0500 )edit

@Masacroso -- No, var vs SR.var is not it, you can test that you would get the same either way.

@Cyrille -- what operating system, what version of Sage, how it was installed, whether is it based on Python 2 or Python 3.

slelievre gravatar imageslelievre ( 2020-04-27 15:51:07 -0500 )edit

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Asked: 2020-04-27 04:18:46 -0500

Seen: 43 times

Last updated: Apr 27