why?? it should be another thing!! 1

[yyhhcart2]

Hi

as you now exp(i*pi)=-1
and as well exp(i*pi)+1 should be 0
but you find it is 1.2246e-016i!!!! in matlab..
does somebody know why???
tnx

 

[IRstuff]

Why would you think that a numerical processor has infinite precision?

TTFN

 

[corus]

The exponential is an infinite series. If you have an infinite amount of time you can get a better answer.

corus

 

[FrancisL]

"If you have an infinite amount of time you can get a better answer"
Not quite, you would also need a computer with an infinite number of bits. That is to say this is a quantisation problem not a time one.

 

[johnwm]

Actually FrancisL since its a converging infinite series any computer will do - you just need a bigger stack of paper in your printer

Good Luck
johnwm
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[zeitghost]

So long as you don't use floating point... the source of the rounding errors.

bcd maths would be better...

 

[IRstuff]

bcd math would have to be floating point as well, to represent cos(). These are irrational numbers and cannot be represented in any format exactly.

TTFN

 

[FrancisL]

That is hat I was trying to say earlier!
Francis

 

[zeitghost]

Indeed.

But bcd math doesn't have the binary/decimal conversion error.

)

 

[IRstuff]

The conversion error is at the limit of the machine's precision, so it really doesn't matter whether you were able to express 0.1 exactly in BCD, when there is an infinite number of cases that BCD doesn't help anyway.

TTFN

 

[johnwm]

You can calculate using scaled integers to any arbitrary precision, as long as the function can be reduced to a converging series. About 20 years ago I was teaching a BASIC programming class in which we calculated pi and e to 100000 places using integer arithmetic.

Took some time to calculate though

Good Luck
johnwm
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