# The Naked Scientists Forum

### Author Topic: calculators  (Read 3469 times)

#### syhprum

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« 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?

#### DoctorBeaver

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« Reply #1 on: 14/09/2007 20:06:00 »
Probably because most are not programmed to handle imaginary numbers.

#### syhprum

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« Reply #2 on: 14/09/2007 20:11:04 »
That I could understand but the cube root of -1 is -1 not imaginary

#### another_someone

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« Reply #3 on: 14/09/2007 21:31:41 »
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?

#### DoctorBeaver

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« Reply #4 on: 14/09/2007 22:45:33 »
That I could understand but the cube root of -1 is -1 not imaginary

Sorry, I mistook cube for square  [:I]

#### lightarrow

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« Reply #5 on: 15/09/2007 01:49:55 »
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?

#### lyner

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##### calculators
« Reply #6 on: 15/09/2007 15:31:59 »
ONE of the cube roots of -1  is REAL
There are two others!! They are complex.
Cubic equations have three roots and they are not necessarily real.
A good calculator would be smart enough to point this out to you.

#### syhprum

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« Reply #7 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.

#### lightarrow

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« Reply #8 on: 15/09/2007 18:26:59 »
ONE of the cube roots of -1  is REAL
There are two others!! They are complex.
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, 21/2 gives 1,414213562 only and not -1,414213562 too?

#### lyner

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##### calculators
« Reply #9 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.

#### DoctorBeaver

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« Reply #10 on: 16/09/2007 08:00:04 »
My spreadsheet programs just give errors

#### syhprum

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« Reply #11 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

#### The Naked Scientists Forum

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« Reply #11 on: 16/09/2007 09:20:15 »