On Oct 6, 2:49 am, Francois Maltey <[email protected]> wrote:
> Hello,
>
> My 15 year old son have an exercice about sqrt.
>
> He must push radix at numerator and decrease it :
>
> Question : 21/sqrt(8)     answer : 21*sqrt(2)/4
> Question : 1/(2-sqrt(3)) answer : 2+sqrt(3)
> Question : is 8/(3-sqrt(13)) + 8/(4+sqrt(13)) is integer
>
> The last result is an integer, So the .radical_simplify() method (from
> maxima) is right.
>
> Is it possible to get from Sage a rational denominator ?

I can't think of a way to do this.  I'm sure there is something in
Maxima... but sometimes people complain about having too many
methods :)

Are you sure this is an integer?  I get


sage: a
-8/(sqrt(13) - 3) + 8/(sqrt(13) + 4)
sage: a.n(prec=100)
-12.159239285498616701223032582
sage: a.n(prec=1000)
-12.1592392854986167012230325815289810825060506779444823259821142623934457587007154109548890494196233491430661827789631884214764985685897692907607467788326455361325559666127122884245418431576190757159417399826773485879966603276698594214556702913883416659412460758017180549650185118315852954478085199043
sage: a.simplify_radical()
-56/(sqrt(13) + 1)
<and multiplying top and bottom by the conjugate gives a non-integer>

But that doesn't change the fact that it would be nice to rationalize
the denominator from inside Sage.

- kcrisman

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