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11172004, 06:22 AM

#1

Member
Registered: Mar 2004
Location: Valencia, espaņa
Distribution: Slack, Gentoo, Custom
Posts: 162
Rep:

please help me do maths :)
Hi
Its funny how you can completely avoid doing any maths despite programming everyday. Anyway i need to learn a bit of maths but its been a long time, can anyone explain how to calculate the sum below ?
N is any number entered.
E is the mathematical symbol 'sum of' (whats this sign called? it will aid future googling
N
E (i+2)
i=1
Sorry about the formatting . . .
The problem is that i don't know what to do with the 'i' and what is this type of maths called so i can do a search and find resources, also does anyone know any good resources for boolean algebra ?
Thanking you all kindly



11172004, 06:39 AM

#2

Senior Member
Registered: Jul 2004
Distribution: Ubuntu 7.04
Posts: 1,990
Rep:

The greek Elike letter you refer to is a sigma.



11172004, 08:18 AM

#3

Moderator
Registered: Jun 2001
Location: UK
Distribution: Gentoo, RHEL, Fedora, Centos
Posts: 43,378

you mean what does it actually mean? it means the sum of all values of i+2 where i is between 1 and N
e.g. N = 4
answer is (1+2) + (2+2) + (3+2) + (4+2) = 3 + 4 + 5 + 6 = 18



11172004, 12:34 PM

#4

Member
Registered: Mar 2004
Location: Valencia, espaņa
Distribution: Slack, Gentoo, Custom
Posts: 162
Original Poster
Rep:

Thanks acid_kewpie,
Perhaps with the answer i could of guessed that one, but i only had the sum and no answer.
Anyone with good links (boolean algebra, boolean logic, karnaugh maps) please feel free post



11182004, 10:05 AM

#5

Member
Registered: Mar 2004
Location: Valencia, espaņa
Distribution: Slack, Gentoo, Custom
Posts: 162
Original Poster
Rep:

Maths tutorials are so bad, i got to get me a book. But in the meantime i got another one
n is any number and i don't understand the relevance of X0. Its newtons algorithm to calculate a square root. So if n = 4, answer = 16 but how to work the answer out ??
X0 = 1
Xi = 0.5 * (N / Xi1 + Xi1)
Thanks for the help



11182004, 10:09 AM

#6

Newbie
Registered: Oct 2003
Posts: 0
Rep:

Quote:
Originally posted by darkRoom
How to work the answer out ??
X0 = 1
Xi = 0.5 * (N / Xi1 + Xi1)

Substitute for i.
X1 = 0.5 * (N / X0 + X0)
X2 = 0.5 * (N / X1 + X1)
...



11182004, 11:50 AM

#7

Member
Registered: Mar 2004
Location: Valencia, espaņa
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Posts: 162
Original Poster
Rep:

I still don't get it, are you sure X2 is really neccessary to calculate the answer ?



11192004, 12:58 AM

#8

LQ Newbie
Registered: Apr 2004
Location: IN
Distribution: Gentoo
Posts: 9
Rep:

In case you're curious, your first problem is a summation and is solved like this:
N
E(i + 2)
i = 1
breaks down into:
Code:
N N
E(i) + E(2) = N(N+1)/2 + 2N
i = 1 i = 1
You could find summations in any Calculus book or by googling for summations:
http://www.google.com/search?q=summations
For your second problem, using 4 as an example isn't a good idea. It's better to use 2. Or 3. And then you can see that you indeed need to go all the way to X2 (in the case of 2) or X3 (in the case of 3).
Last edited by gorzuate; 11192004 at 01:20 AM.



11192004, 02:23 AM

#9

Member
Registered: Aug 2004
Location: Albany, Western Australia
Distribution: Mageia 2, SME Server 8
Posts: 617
Rep:

omg
this will be the second book I've recommended in as many days
maybe we should link to Hari's Book site
just kidding Mods
Never was that good at maths, my old maths teacher will confirm that. However during my accounting studies we had to use a text book even I could follow. it is ...
Business Maths and Statistics
by Peter Waxman
ISBN 0 7248 0138 3
pub by Prentice Hall
your first formula looked similar to one we use to calculate compounding interest.
Anyway I dont know whether you'll be able to buy it outside Australia, but you could try Amazon.
hope this helps
live long and prosper
floppy



11192004, 08:32 AM

#10

Member
Registered: Sep 2003
Location: Australia
Distribution: Fedora Core 3 / Mandrake 10.1 / Gentoo 2005.0
Posts: 100
Rep:

With reference to Newton's method, it is iterative (repetitive, ie X2, X3, X4). The answer usually gets better and converges. But it's not failsafe. It fails when there's no answer or results diverge.



11212004, 12:18 AM

#11

LQ Newbie
Registered: Nov 2004
Location: Sliven, Bulgaria
Distribution: SuSE 9.0
Posts: 5
Rep:

Re: please help me do maths :)
Quote:
Originally posted by darkRoom
Hi
Its funny how you can completely avoid doing any maths despite programming everyday. Anyway i need to learn a bit of maths but its been a long time, can anyone explain how to calculate the sum below ?
N is any number entered.
E is the mathematical symbol 'sum of' (whats this sign called? it will aid future googling
N
E (i+2)
i=1
Sorry about the formatting . . .
The problem is that i don't know what to do with the 'i' and what is this type of maths called so i can do a search and find resources, also does anyone know any good resources for boolean algebra ?
Thanking you all kindly

The name of the Summation sign (your E) is the Greek Letter "Sigma". For those who don't know, it looks like the number 3 backwards, and all 4 arms straight lines.
Of course, when you get into Calculus, the Sigma becomes the Integration Sign. But whatever terrible things happen in your life caused by Calculus serves you right!



03152005, 03:28 PM

#12

LQ Newbie
Registered: Nov 2004
Location: Sliven, Bulgaria
Distribution: SuSE 9.0
Posts: 5
Rep:

Σ! There it is! In Windoze, you just need to install the Greek Alphabet, which is very easy. (Don't ask me hhow to do it in Linux, but I'm sure you know how!) Then it's the letter "B" on your English Language Keyboard.



03152005, 04:43 PM

#13

Senior Member
Registered: Dec 2004
Location: Olympia, WA, USA
Distribution: Fedora, (K)Ubuntu
Posts: 4,147

Re: please help me do maths :)
Quote:
Originally posted by darkRoom
Hi
Its funny how you can completely avoid doing any maths despite programming everyday.
...

You don't say which language you use for programming, but  to pick a simple one  what you're looking at is a "for" loop. In this case: (This is psudocode, buut you should 'get it.')
Code:
Sum := 0
for i = 1..N
Sum := Sum + i + 2
next
print Sum
For the other example:
Quote:
X0 = 1
Xi = 0.5 * (N / Xi1 + Xi1)

Code:
X := N/4
while (X != 1)
Y := 0.5 * (N/(X  1) + X1)
if abs(X  Y) < 0.00001 break
X := Y
next
print Y
Generally, most simple maths expressions are almost directly expressable in computer code.
(In fact, the APL computer language was designed as a mathematical language for stating proofs before it was implimented as a computer code. But that's off the subject here.)
Hope this helps.



03152005, 06:31 PM

#14

LQ Newbie
Registered: Apr 2004
Location: midwest
Distribution: fedora core 1
Posts: 12
Rep:

maths?



03162005, 03:47 AM

#15

LQ Newbie
Registered: Nov 2004
Location: Sliven, Bulgaria
Distribution: SuSE 9.0
Posts: 5
Rep:

Yeah! maths!
You know, that subject that is easy until one hits Differential Equations?



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