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## #1 2012-10-25 13:46:44

Kenjiska
Guest

### Factorial

Please,tell me the value of these-
i !
(-1) !
(1+i) !
(.1) !

## #2 2012-10-25 15:45:29

bobbym

Offline

### Re: Factorial

Hi;

(-1) ! does not exist. All the negative integers of the factorial function are equal to infinity.

I would use a Taylor series for some of them. How much accuracy do you need.

Basically though you would use a computer or Wolfram Alpha to look those up. If your teacher wants to see some method then how is it you do not know that method? If I use series expansion he/she may not want that method used. So provide me with what method is to be used.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #3 2012-10-25 19:19:34

Kenjiska
Guest

### Re: Factorial

Show me using the taylor series

## #4 2012-10-25 20:43:25

bobbym

Offline

### Re: Factorial

Hi;

Those are all difficult but here goes nothing!

Let's try (.1)! first. For that we use a series and a trick.

It is in nested or Horner form for fast computation. The series is best for values >=5 so we put in z = 5.1

We take the exponential of both sides and get.

Now to get .1! we use a simple relation:

So

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #5 2012-10-25 21:45:46

Kenjiska
Guest

### Re: Factorial

What about the others
(1+i)!
i !

## #6 2012-10-25 22:41:49

bobbym

Offline

### Re: Factorial

For i! use this truncated series:

Substituting z = i you get

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #7 2012-10-26 03:25:29

zetafunc.
Guest

### Re: Factorial

Also, for (1+i)!, you can find that using bobbym's answer, since