> On Tue, 20 Sep 2011 10:47:13 +0200, Roman Reiner <lim### [at] gmxde> wrote:
>
>> Invisible <voi### [at] devnull> wrote:
>>> On 20/09/2011 02:06 AM, Darren New wrote:
>>> > On 9/19/2011 11:20, Orchid XP v8 wrote:
>>> >> Fact is, 0 * infinity = 0, so it's not a sensible answer.
>>> >
>>> > I can't imagine how you can say dividing by zero is undefined, but
>>> then
>>> > go and define multiplying zero by infinity. :-)
>>>
>>> If you multiply *anything* by zero, the result is always zero. This
>>> isn't exactly news. We're not "defining" anything, we're just using the
>>> pre-existing definition of how multiplication by zero works.
>>
>> You're wrong there. 0 * inf = 0 is indeed a definition as the result
>> of the
>> left-hand side is undefined in the same manner as dividing by zero is
>> (actually,
>> the concepts of multiplication and division are mathematically the
>> very same
>> thing).
>> see, if you define 1/0 = inf, and treat 0 and inf as ordinary numbers,
>> then 0 *
>> inf = 0/0 = 1 contrary to your claim. This contradiction is the result
>> of using
>> inf as a number when, in fact, it isn't.
>>
>> Regards Roman
>>
>>
>
> So there needs to be a rule of order - similar to doing calculations in
> brackets first.
> What I mean is in th case of 0/0 - which rule should be applied first?
> A) 0/anything =0
> B) anything divided by itself =1
> C) anything divided by 0 is undefined
>
>
>
The exact case depends on /how/ you reatch 0/0.

If you follow a x/x, (x^n)/x, x/(x^n)... suite, then you have the case B 
and the result is 1. As the value of x become infinitesimally small, 
your result stay, or converge to 1.
If you have 0/x, "x" been about any expression, then the result should 
be zero.
In other cases, it's undefined, +infinity or -infinity.

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