Easy question about exact results on screen
06-01-2016, 03:06 PM
Post: #1
 PedroML Junior Member Posts: 5 Joined: Apr 2016
Easy question about exact results on screen
Trying to get zeros of this polinomy: x^3-x^2+0.5x-0.125, which settings allows me to get the exac form :1/2,(1+sqrt(3)*i)/4,(1-sqrt(3)*i)/4)??
The exact question would be, which settings bring the exact "answer" without decimals?

Thank you again!
Pedro ML
06-01-2016, 03:21 PM
Post: #2
 Didier Lachieze Senior Member Posts: 1,508 Joined: Dec 2013
RE: Easy question about exact results on screen
To get exact results you need to use exact fractions for the numbers (for ex. 5/10) and not approximate decimal numbers such as 0.5
In CAS mode:
Code:
cSolve(x^3-x^2+(5/10)*x-(125/1000)=0,x)
will provide the exact result you're expecting.
06-01-2016, 03:46 PM (This post was last modified: 06-01-2016 03:49 PM by salvomic.)
Post: #3
 salvomic Senior Member Posts: 1,394 Joined: Jan 2015
RE: Easy question about exact results on screen
if you use (in CAS: in Home I get [] -why?- ...)
cZeros(x^3-x^2+(½)*x-(⅛))
you get
[$$\frac{1}{2} \ \frac{1}{4}*(\sqrt{3}*i+1) \ \frac{1}{4}*(-\sqrt{3}*i+1)$$]

As you know, If you input .05, .0125 you'll get only [0.5]

I'm using CAS and check in the "complex" and "exact" items in Shift-CAS Settings...

Salvo

∫aL√0mic (IT9CLU) :: HP Prime 50g 41CX 71b 42s 39s 35s 12C 15C - DM42, DM41X - WP34s Prime Soft. Lib
06-01-2016, 04:23 PM
Post: #4
 PedroML Junior Member Posts: 5 Joined: Apr 2016
RE: Easy question about exact results on screen
Thank you so much Salvo, Didier.
Both answers are great, and incredible fast!!!

Best regards!
06-01-2016, 04:33 PM (This post was last modified: 06-01-2016 04:41 PM by salvomic.)
Post: #5
 salvomic Senior Member Posts: 1,394 Joined: Jan 2015
RE: Easy question about exact results on screen
(06-01-2016 04:23 PM)PedroML Wrote:  Thank you so much Salvo, Didier.
Both answers are great, and incredible fast!!!

Best regards!

you're welcome :-)

also, Pedro, you can use (if you want) 0.5 and 1.125, and then, after getting the approx results, use QPI program (QPI by Han) to obtain the same symbolic results...

Hovewer, as Didier said, it's better use fractions instead of decimals for best results.

Salvo

Attached File(s) Thumbnail(s)

∫aL√0mic (IT9CLU) :: HP Prime 50g 41CX 71b 42s 39s 35s 12C 15C - DM42, DM41X - WP34s Prime Soft. Lib
 « Next Oldest | Next Newest »

User(s) browsing this thread: 1 Guest(s)