New Topic

GeoGebra Topic Question English

Category English

proper fraction by default

Solving problems involving fractions

Dynamic text using a fraction in a product

Comments

Participants

Subscribers

Votes

Views

3027

Is there a "proper fraction" command, like in TI-Nspire CAS?

Constantinos shared this question 6 years ago

Answered

Hi to all,

I 'm a graduate teacher and I want to see if I students can use GeoGebra to calculate the derivatives of algebraic expressions.

For example, when I 'm looking for the derivative of f(x)=(x + sqrt(x)) / x²

GeoGebra yields f'(x)=(1 + 1 / 2 / x^(1 / 2)) / x^(2) - (2 * (x + x^(1 / 2)) / x^(3)).

This is very confusing for the students.

How can I make Geogebra yield f'(x)=-1/x^2 - (3/2)x^(-5/2) ?

In other words, how can I make GeoGebra to break the output properly into simple separate fractions (=present the output into a polynomial form)?

In TI-Nspire CAS, there is a command called "proper function" that does this work.

The same question

Comments (5)

rami ● 6 years ago

Hi,

In some cases help:

Simplify[]

Factor[]

Expand

Raymond

Reply URL

chaffeur ● 6 years ago

For example, when I 'm looking for the derivative of f(x)=(x + sqrt(x)) / x²

GeoGebra yields f'(x)=(1 + 1 / 2 / x^(1 / 2)) / x^(2) - (2 * (x + x^(1 / 2)) / x^(3)).

I don't believe, so! In fact, last GG version 4.4.40 performs the shown results: r(x), s(x). While, by algebraically manipulating the given function as per p(x), its derivative q(x) is better simplified.

Cheers

Philippe

https://ggbm.at/567445 1a3090abfc40d79f7c4c26fcdf77cf33

Files: 07.png

Reply URL

Constantinos ● 6 years ago

Thanks for the replies to everybody

@ Noel:

Yes, PartialFractions doesn't help.

@ Raymond:

I tried them all, nothing useful came out.

@ chaffeur:

I did get the same results q(x) and s(x).

q(x) is more acceptable, but still not expressed as a polynomial with the proper negative exponents notation.

If you try to get the answers using CAS, you will get the weird looking expression I was talking about. See CAS line 3 on my screenshot.

When I deactivated the option "Show rational exponents as roots" in the Advanced Options, I got the result shown in CAS line 1, which is much better than all the other ones.

I tried to simplify that in CAS line 2, but the outcome doesn't look nice.

So the problem is after all that I can't make GeoGebra to properly simplify algebraic expressions containing fractional exponents. As you can see in CAS line 4,

I can't make GeoGebra to yield x^(5/2) for the operation (x^(1/2))*x^2. 4fdd86648b34e3967151333f9bfd45f8

Files: Image3.jpg

Reply URL

chaffeur ● 6 years ago

Hi Constantinos,

please, see my photo-comment underneath. Source comes from your previous post.

Cheers

Philippe 9a284577f03a8f47cb5bdbd91640c3f3

Files: 09.png

Reply URL

Constantinos ● 6 years ago

Thanks Philippe,

I hope too that developers will see this topic and take action! :wink:

Reply URL