Now this is a simplification:
11-17-2017, 04:49 PM
Post: #1
 DrD Senior Member Posts: 1,132 Joined: Feb 2014
Now this is a simplification:
[CAS]
diff((3*x^2-4)^100,x); ==> 100*3*2*x*(3*x^2-4)^99

This was fun:
Code:
simplify([b]diff((3*x^2-4)^100,x[/b])); //  ... quick, SHUT THE DAMN DOOR !!!! PRINT(Ans);

This seems MUCH simpler than simplify():
collect(diff((3*x^2-4)^100,x)); ==> 600*x*(3*x^2-4)^99

Now try this (automatically simplified (collected) result):
y:=diff((3*x^2-4)^100,x); ==> 600*x*(3*x^2-4)^99

Without assignment the expression produces a non-collected result. By simply assigning the expression to a variable, a collected result is saved.

-FYI-
11-17-2017, 06:24 PM
Post: #2
 parisse Senior Member Posts: 1,136 Joined: Dec 2013
RE: Now this is a simplification:
simplify expands expressions, some rewriting commands don't and sometimes it's better not to expand, like regroup here. There is no magic way to simplify an expression, for example what's simpler (x^7-1)/(x-1) or the expanded simplified form?
11-17-2017, 07:45 PM
Post: #3
 DrD Senior Member Posts: 1,132 Joined: Feb 2014
RE: Now this is a simplification:
Can one test for, "what is simpler" be readability?

Which is simpler in your eyes:

600*x*(3*x^2-4)^99

-or-

[attachment=5335]
And that's only the first page!
11-17-2017, 09:08 PM (This post was last modified: 11-17-2017 09:09 PM by Han.)
Post: #4
 Han Senior Member Posts: 1,843 Joined: Dec 2013
RE: Now this is a simplification:
(11-17-2017 07:45 PM)DrD Wrote:  Can one test for, "what is simpler" be readability?

Which is simpler in your eyes:

600*x*(3*x^2-4)^99

-or-

And that's only the first page!

Well that all depends. Even though the second form takes more than a single screen, it's more simplified because all terms are monomials, and hence "simplified." This topic comes up every now and then, and in the end it really boils down to the same thing: everyone's view on "simplified" is different. Even with the same user, it can have different meaning.

(x-1)^7/(x-1) might look simplified because it takes up little screen space. Yet it's not simplified because (x-1)^7/(x-1) = x^6 + x^5 + x^4 + x^3 + x^2 + x + 1 (for x not equal to 1) which can be written as $$\sum_{i=1}^6 x^i$$. Each of these forms has their own uses depending on the user's situation.

HP should just get rid of the simplify command altogether; users should be forced to use the relevant algebraic manipulation command that they need.

Graph 3D | QPI | SolveSys
11-18-2017, 12:13 PM
Post: #5
 webmasterpdx Senior Member Posts: 541 Joined: Sep 2015
RE: Now this is a simplification:
Simplification is just perspective and context. Parisse is correct.
You really need a different word, like expand/compress/collect, etc.. to reflect what you really want it to do.
11-18-2017, 12:25 PM
Post: #6
 Arno K Senior Member Posts: 442 Joined: Mar 2015
RE: Now this is a simplification:
(11-18-2017 12:13 PM)webmasterpdx Wrote:  Simplification is just perspective and context. Parisse is correct.
You really need a different word, like expand/compress/collect, etc.. to reflect what you really want it to do.

So perhaps a good feature request would be: Give us Expand, Collect and Algebra in the Cas Soft-menu.
Arno
11-18-2017, 12:31 PM
Post: #7
 salvomic Senior Member Posts: 1,392 Joined: Jan 2015
RE: Now this is a simplification:
(11-18-2017 12:25 PM)Arno K Wrote:  So perhaps a good feature request would be: Give us Expand, Collect and Algebra in the Cas Soft-menu.
Arno

and surely also QPI() and regroup() both in Home and CAS Soft-Menu

∫aL√0mic (IT9CLU) :: HP Prime 50g 41CX 71b 42s 39s 35s 12C 15C - DM42, DM41X - WP34s Prime Soft. Lib
11-18-2017, 12:44 PM
Post: #8
 DrD Senior Member Posts: 1,132 Joined: Feb 2014
RE: Now this is a simplification:
(11-18-2017 12:13 PM)webmasterpdx Wrote:  Simplification is just perspective and context. Parisse is correct.
You really need a different word, like expand/compress/collect, etc.. to reflect what you really want it to do.

Interesting in that we have at least three built in "perspectives" on the context:
{none, minimum, maximum}, which is not to mention the actual simplify() command, which has this particular perspective: "Simplifies an expression."

WTH?
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