Simplify_full() and collect() together

asked 2022-12-15 11:06:06 +0100

Boyko_Bu
51 ●1 ●1 ●7

updated 2022-12-15 18:18:13 +0100

Dear all,

I am a novice with sagemath, and I use only a very small subset of its functionalities. I need to simplify the following expression, without using definitions:

var('c,f')
p_star_1 = ( (c+1)*f^2 - (2*c +1)*f - c - f ) / 2*(f^2-*2*f-1)

Here, I report the output of p_star_1, which in the real program is p_star_1 = something.simplify_full(). I would like to express this as:

 p_star_1 = c/2 + (2-f)*(1+ f)/(2*(1+2*f-f^2))

But using collect.(c) is not sufficient! How can I do this?

EDIT: I corrected the expression again, sorry.

Comments

Your expression p_star_1 = ( (c+1)*f^2 - (2*c +1)*f - c - f ) / 2*(f^2-*2f-1) is not accepted by Sage. Do you mean p_star_1 = ( (c+1)*f^2 - (2*c +1)*f - c - f ) / 2*(f^2-2*f-1) ? Or perhaps p_star_1 = ( (c+1)*f^2 - (2*c +1)*f - c - f ) / 2*(f^2-2*f(-1)) (not quite the same thing...).

I am not a Sibyl... `

Emmanuel Charpentier ( 2022-12-15 13:33:49 +0100 )edit

I meant the former, I corrected

Boyko_Bu ( 2022-12-15 15:41:17 +0100 )edit

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answered 2022-12-15 17:57:36 +0100

Emmanuel Charpentier
7744 ●6 ●50 ●153

updated 2022-12-15 17:58:05 +0100

p_star_1 znd the expression you seek are not equal :

sage: SEx=c/2 + (f^2  - f - 2)/(2*(f^2  - 2*f - 1 ))
sage: (p_star_1-SEx).expand().is_zero()
False

which is more obvious if you ask a typeset form :

sage: view((p_star_1/SEx).expand().factor())

which displays :

$$ \frac{{\left(c f^{2} - 2 \, c f + f^{2} - c - 2 \, f\right)} {\left(f^{2} - 2 \, f - 1\right)}^{2}}{c f^{2} - 2 \, c f + f^{2} - c - f - 2} $$

The problem might be

sage: p_star_1.operands()
[(c + 1)*f^2 - (2*c + 1)*f - c - f, f^2 - 2*f - 1, 1/2]
sage: p_star_1.operands()[0].collect(f)
(c + 1)*f^2 - 2*(c + 1)*f - c

Maybe another typo ?

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Comments

Yeah, probably, I updated, I am copying manually from Jupyter to here, not simple, let me know if now works, I can't see any other error at the moment.

Boyko_Bu ( 2022-12-15 18:19:46 +0100 )edit

I am copying manually from Jupyter to here

Copy 'n paste doesn't work ?

let me know if now works.

The present site lets you expect that some people will take time to build answers to your questions. YOU CAN'T expect them to guess what the question is...

</fuming>

Emmanuel Charpentier ( 2022-12-16 08:22:16 +0100 )edit

You can fume as much as you want, OR, you can imagine do I feel losing A WHOLE DAY working with software that CANNOT RECOGNIZE that two terms that sum to one ARE a simplification. Hence, DON'T be arrogant just because you know I am a newbie, understand my position, and look at the question now. If it still doesn't work, I'll update again.

Boyko_Bu ( 2022-12-16 11:01:40 +0100 )edit

The two expressions (in their various versions) you gave us are NOT a simplification of each other.

Try to copy'n paste the expressions printed in Jupyter to your message.

Yelling I'm arrogant won't fix your copy n'paste result...

Emmanuel Charpentier ( 2022-12-17 07:49:39 +0100 )edit

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