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On 2004-11-14T08:30:53+00:00 Kmorning wrote:

It looks like calc is unable to evaluate odd roots (a number raised to the 
power of 1/3,1/5,1/7,...etc).  For instance if you type in as a formula 
-8^(1/3), calc returns #VALUE when the answer should be -2.  It looks like any 
negative number you raise to a fractional exponent can't be evaluated.  For 
even roots this should be expected since imaginary values would result, 
however odd roots should result in real values.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/openoffice.org/+bug/264345/comments/0

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On 2004-11-15T09:05:53+00:00 Frank-l wrote:

Hi,

it's the same problem as described in Issue 24271. Therefore I close this one as
double.

Frank

*** This issue has been marked as a duplicate of 24271 ***

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https://bugs.launchpad.net/ubuntu/+source/openoffice.org/+bug/264345/comments/1

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On 2004-11-15T09:06:09+00:00 Frank-l wrote:

closed double

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https://bugs.launchpad.net/ubuntu/+source/openoffice.org/+bug/264345/comments/2

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On 2004-11-15T09:31:09+00:00 Frank-l wrote:

Sorry,

not a double.

Frank

Reply at:
https://bugs.launchpad.net/ubuntu/+source/openoffice.org/+bug/264345/comments/3

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On 2004-11-15T09:32:03+00:00 Frank-l wrote:

Hi Eike,

please have a look.

Frank

Reply at:
https://bugs.launchpad.net/ubuntu/+source/openoffice.org/+bug/264345/comments/4

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On 2004-11-15T10:23:06+00:00 Niklas-nebel wrote:

This should be changed, but it's not inportant enough for target "2.0".

Reply at:
https://bugs.launchpad.net/ubuntu/+source/openoffice.org/+bug/264345/comments/5

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On 2005-02-03T20:10:29+00:00 Cs213006 wrote:

Bug repeated in OOo1.1.3/Linux and 680m74 on WinXP

Reply at:
https://bugs.launchpad.net/ubuntu/+source/openoffice.org/+bug/264345/comments/6

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On 2007-02-09T23:28:58+00:00 Cbx550f wrote:

Repeated in 2.0.3 Linux

Reply at:
https://bugs.launchpad.net/ubuntu/+source/openoffice.org/+bug/264345/comments/7

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On 2007-02-22T22:29:35+00:00 Rb-henschel wrote:

Why do you want to change it? It is dangerous to calculate like (-8)^(1/3)=-2.
Look at this:
(-8)^(1/3)=(-8)^(2/6)=((-8)^2))^(1/6)=64^(1/6)=2

If you use fractions in exponents and want to keep the rules for exponents, than
you cannot allow negative base. And ^ and POWER calculate with exponents.

There are other opinions, but then you are speaking of a cube root, which would
be a new function in Calc.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/openoffice.org/+bug/264345/comments/8

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On 2007-02-22T22:30:42+00:00 Rb-henschel wrote:

*** Issue 74782 has been marked as a duplicate of this issue. ***

Reply at:
https://bugs.launchpad.net/ubuntu/+source/openoffice.org/+bug/264345/comments/9

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On 2008-09-30T18:12:56+00:00 Rb-henschel wrote:

*** Issue 94487 has been marked as a duplicate of this issue. ***

Reply at:
https://bugs.launchpad.net/ubuntu/+source/openoffice.org/+bug/264345/comments/22

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On 2009-04-15T04:42:30+00:00 Mikekaganski wrote:

The bug persists in OOo 3.0.1/WinXP.

It leads to incompatibility with MS Excel and thus, to difficulties in 
migration.

The general math rule says that "For odd values of n, every negative number has 
a real negative nth root" (http://en.wikipedia.org/wiki/Nth_root). And it's not 
correct to spaculate that "(-8)^(1/3)=(-8)^(2/6)=((-8)^2))^(1/6)=64^(1/6)=2". 
This speculation is a sort of sophism that masks the fact that there are more 
than one nth roots. When you make any transformations of powers you must take 
into account the possible loss of some roots or introduction of new roots. The 
correct result of "sqrt(x)" should be a multitude of two (possibly complex) 
numbers, not a single number. As we cannot return such a result in a 
spreadsheet we agree to see only positive answer, but it doesn't mean that we 
don't deserve to get correct negative real number as a cube root of a negative 
number.

To be specific: x != sqrt(x^2), because, strictly speaking, sqrt(x^2) = {x, -
x}. So (-8)^(1/3) = (-8)^(2/6) [only if you calculate 2/6 _before_ you 
calculate the exponent] != ((-8)^2))^(1/6), because here in the last case the 
base is raised to 2nd power and then the 6th root is taken, and the extra "2" 
brings new roots here (positive ones).

As it can be seen in Issue 24271 (that was erroneously treated as duplicate to 
this one), the OOo team makes it's best to maintain compatibility with its main 
competitor. This approach has very strong base and is honored sometimes even if 
there's a mistake in th MS Office to let users migrate painlessly. But in this 
case you refuse to make changes that not only consistent with MS Excel, but 
also mathematically correct!

[Workaround] for those who want to find the cube root:
SIGN(X)*ABS(X)^(1/3)

Reply at:
https://bugs.launchpad.net/ubuntu/+source/openoffice.org/+bug/264345/comments/23


** Changed in: openoffice
   Importance: Unknown => Low

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