Divide by zero

[Farabi]

Okay I am stupid, I though that everything divided by zero have to be zero because everything mul by zero must be zero.

So lets take an example.

1/10 = 0.1
but 1/(0.1)=10

So the conclusion is, the tinier the divisor, the bigger the result.
Lets take another example

1/(1/100) Also you can type it as 1/(0.01) it will yield result 100
So do 1/(0.00000001) it will result 10000000

So what it we divide it with zero? Yes. It would be infinity. I was stupid, really stupid. I know this when I on hi-school but never understand it.

[Vortex]

Hi Onan,

The result of division by 0 is undefined :

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x \ 0 = not defined   ( x is a member of the real number set. )

You need to careful with zero. Consider this :

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0 \ 0 = ? ( again undefined )

0 \ 0 = 0 is false. Here is a trick :

( 0 \ 0 ) * 5 = ( 0 \ 0 ) * 10

0 * 5 = 0 * 10     ->  0 * 5 = 0    ,    0 * 10 = 0

Trying to simplify by 0 ( division by 0 ) :

5 = 10 or 1 = 2 which is not true.

Working on the division by 0 problem, the correct approach is to use limits :

lim x -> 0+  ( a \ x ) = + ∞

lim x -> 0-  ( a \ x ) = - ∞

lim x -> 0  ( a \ x ) = undefined

Some examples :

i) lim x -> 0+  ( a \ x ) = + ∞

5 \ 0.001 = 5000

5 \ 0.000001 = 5000000

5 \ 0.0000000001 = 50000000000

...

ii) lim x -> 0-  ( a \ x ) = - ∞

5 \ -0.001 = -5000

5 \ -0.000001 = -5000000

5 \ -0.0000000001 = -50000000000

...

[jj2007]

Or watch in Olly what you get - it's called a BAD number :bg

Code Select Expand

include \masm32\include\masm32rt.inc

.code
start: fldz
fldz
fdiv
exit
end start


[dedndave]

technically, any value divided by zero is "undefined"
however, in calculus, it is sometimes convenient to assign it a value of correctly signed infinity   :P

[mineiro]

Zero means "nothing", but is represented as one simbol. Zero are hold places simbolics.

[Farabi]

Vortex:
:U Thank I think I got it.

[vanjast]

however, in calculus, it is sometimes convenient to assign it a value of correctly signed infinity   :P

.. a defined 'indefinite'...  :eek

if you think of it 'logically'..

If you take something, and you divide it into zero pieces... you end up with either 1 or 0 pieces (hence Binary is the way  :green2),... not suddenly a gazillion pieces. (This sort of thing only happens in magical biblical scripts)  :bg

[Vortex]

Hi vanjast,

If you take something, and you divide it into zero pieces... you end up with either 1 or 0 pieces (hence Binary is the way  ),... not suddenly a gazillion pieces. (This sort of thing only happens in magical biblical scripts)

Nice comment. You reminded me Schrödinger's cat remaining both alive and dead.

[vanjast]

It could mean that what you observe is actually 'what is', and visa versa..
:wink

[xanatose]

I guess, it would also depends on the set of data.

Consider the formula for RSI (relative strength index).

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RSI = 100 - 100/(1 + (Average Gain / Average Loss))


Which gives a value between 0 and 100 inclusive.

What happens if there is no loss in the set of data. Sure one can go to the undefined route here. But what I do instead is:

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if(0 == Average Gain) {
  if(0 == Average Loss) {
    RSI = 50;
  } else {
    RSI = 0;
  }
} else if(0 == Average Loss) {
  RSI = 100;
} else {
  RSI = 100 - 100/(1 + (Average Gain / Average Loss))
}

Mathematically incorrect. But avoids a division by zero,while giving a usable result.

If the average gain is equal to the average loss, then RSI = 50
If the average gain is zero, the RSI is zero.
If the average loss is zero, then RSI will tend to its maximum value 100
Otherwise use the formula.

[daydreamer]

put on Pet Shop boys "divide by zero" while solve is:)
so if I have a divide inside an algo, I say I need to define divide by zero etc by what works best for what is best to produce from that algo
a related problem is also trigo tan endsup to be 90 degrees