Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: syhprum on 14/09/2007 17:15:13

Title: calculators
Post by: syhprum on 14/09/2007 17:15:13

whenever I get to test a pocket scientific calculator I ask it to evaluate the cube root of -1, some manage OK but most give up the ghost why?

Title: calculators
Post by: DoctorBeaver on 14/09/2007 20:06:00

Probably because most are not programmed to handle imaginary numbers.

Title: calculators
Post by: syhprum on 14/09/2007 20:11:04

That I could understand but the cube root of -1 is -1 not imaginary

Title: calculators
Post by: another_someone on 14/09/2007 21:31:41

Quote from: syhprum on 14/09/2007 20:11:04

That I could understand but the cube root of -1 is -1 not imaginary

This is true, but did the programmer who programmed the calculator understand that?

Title: calculators
Post by: DoctorBeaver on 14/09/2007 22:45:33

Quote from: syhprum on 14/09/2007 20:11:04

That I could understand but the cube root of -1 is -1 not imaginary

Sorry, I mistook cube for square  [:I]

Title: calculators
Post by: lightarrow on 15/09/2007 01:49:55

Quote from: another_someone on 14/09/2007 21:31:41

Quote from: syhprum on 14/09/2007 20:11:04

That I could understand but the cube root of -1 is -1 not imaginary

This is true, but did the programmer who programmed the calculator understand that?

[;D]

Title: calculators
Post by: lyner on 15/09/2007 15:31:59

ONE of the cube roots of -1  is REAL
There are two others!! They are complex.
There's plenty of links on google for this.
Cubic equations have three roots and they are not necessarily real.
A good calculator would be smart enough to point this out to you.

Title: calculators
Post by: syhprum on 15/09/2007 18:02:19

I have downloaded two software calculators that are not freeware and they both give the answer as -1 but the calculator that comes with Windows XP cannot cope with it.

Title: calculators
Post by: lightarrow on 15/09/2007 18:26:59

Quote from: sophiecentaur on 15/09/2007 15:31:59

ONE of the cube roots of -1  is REAL
There are two others!! They are complex.
There's plenty of links on google for this.
Cubic equations have three roots and they are not necessarily real.
A good calculator would be smart enough to point this out to you.

Ok, but a very good calculator would be smart enough to give all the three values...
If it's limited to real values only, then it should give -1 as result. You cannot say that, actually, it can't answer because there are more than one solution: why, then, 2^1/2 gives 1,414213562 only and not -1,414213562 too?

Title: calculators
Post by: lyner on 15/09/2007 22:49:19

A really smart machine would have to  give some extra comments about validity of results and, as you say, lists of alternative answers.
Wolfram's Mathematica is one bit of software which works in the right direction. It's annoyingly clever at all the Maths I learned at School and later.

Title: calculators
Post by: DoctorBeaver on 16/09/2007 08:00:04

My spreadsheet programs just give errors  [:(]

Title: calculators
Post by: syhprum on 16/09/2007 09:20:15

http://mathworld.wolfram.com/

This is a good start point to see what Wolfram's Mathematica is all about