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20180515
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CAS question
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Hallo,
I do not understand why in CAS window
sqrt(x  1) * sqrt(x  2)
equals
sqrt(x^2  3 * x + 2) ?
blondyn
Files:
sqrt02.ggb
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Looks like a bug.I've looped your question to the Developers
not only in CAS . Try Simplify(sqrt(x  1) sqrt(x  2)) in algebra view
It's not as simple as it appears; sqrt(x^2  3 * x + 2) is correct for some of the domain (for example x = 0)
We've made an improvement for the next release (v466) but there will still be "surprising" examples :)
If you need it just as a function then you can avoid the problems by using "Keep Input"
but the graph of f and simplify(f) has only one point in common
I thougth that GG suposse that the numbers are real in functions
(and CAS commands eg Simplify)
and the Algebra View eg
but the problem is in GG algebra view also
my graph is done only with algebra view
f(x)=sqrt(x1) sqrt(x2) (green graph)
simplify(f) (red graph)
Thank you for answers.
Maple has not the problem.
then it seems to me that sqrt(x1) sqrt(x2)>(sgn(x1)+sgn(x2))/2 sqrt(x^23x+2) because usually to simplify expands the domain
v466 online now
Dear Michael,
Thank you very much for the improvement. It is a bit better than before but
there are still a few issues to resolve. Please have a look at the
attachment I included previously: Maple_sqrt.pdf
I have tried also other CAS programs: Wolfram Alpha and MuPAD Light  they
all produce the same graphs as Maple.
I lecture about GeoGebra to high school teachers as part of a national
project IT Academia. They love GoeGebra and would like to learn more about
it, they even want to use it in their curriculum.
Unfortunately, we don't teach complex numbers at high schools here. Thus, we
have to find a suitable way how to use GeoGebra in teaching within these
limits.
I thank you once more for the great work you're doing for the community of
GeoGebra users.
Best,
Jozef
It's a similar problem to eg
You can use the Keep Input Tool to disable the automatic simplifying
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