# Numerical analysis: What are N, N*, Z and Q????

• Jul 3rd 2009, 02:36 PM
Julian.Ignacio
Numerical analysis: What are N, N*, Z and Q????
I can't seem to understand what they are..this is what the teacher explained us

N=Set of natural numbers
N*=??? I dunno....
Z=set of intergers...
Q= Set of rational number (Most complex one for the matter...)
• Jul 3rd 2009, 02:40 PM
mr fantastic
Quote:

Originally Posted by Julian.Ignacio
I can't seem to understand what they are..this is what the teacher explained us

N=Set of natural numbers
N*=??? I dunno....
Z=set of intergers...
Q= Set of rational number (Most complex one for the matter...)

N* possibly means the set of natural numbers and the number 0 (but you should ask your teacher). As for the meanings of the others ....

Try Googling for:

natural numbers

integers

rational number
• Jul 3rd 2009, 02:41 PM
Julian.Ignacio
Well...I do understand the descriptions but...when used In sentences I just simply can't.
• Jul 4th 2009, 01:44 AM
Raoh
Quote:

Originally Posted by mr fantastic
N* possibly means the set of natural numbers and the number 0 (but you should ask your teacher). As for the meanings of the others ....

$\displaystyle \mathbb{N}^{*}$ is the set of natural numbers without a zero.
• Jul 4th 2009, 12:06 PM
RyanMoi
All "numbers" fall under the category of complex numbers (C).

Within C, you also have categories for numbers which are either purely imaginary (I) or real (R).

All of R can be described as being either rational (Q) or irrational (examples: pi, euler's number, etc).

Q are numbers which can be described in terms of a fraction form: $\displaystyle a/b$.
Example: 122 can be written as 122/1; 1.33... can be written as 4/3

Within Q, you can describe integers Z (all Q whose denominator is 1; examples: 12, 2, -456), natural numbers N (all positive integers excluding 0), and N* (all positive integers including 0).

These are just ways of describing numbers in analysis. For example, if an expression is described as being in N, you will be dealing with multiples of whole numbers (aka integers).
• Jul 4th 2009, 12:22 PM
Raoh
$\displaystyle \mathbb{N} =\left \{ 0,1,2... \right \}$
$\displaystyle \mathbb{N^{*}} =\left \{ 1,2,3... \right \}$
i believe zero is considered as a natural number.
• Jul 4th 2009, 02:06 PM
mr fantastic
Quote:

Originally Posted by Raoh
$\displaystyle \mathbb{N} =\left \{ 0,1,2... \right \}$
$\displaystyle \mathbb{N^{*}} =\left \{ 1,2,3... \right \}$
i believe zero is considered as a natural number.

Some reading: Is zero a natural number?@Everything2.com

Counting from zero is not a natural thing to do. It takes a certain level of sophistication to realise that you can have a set containing zero elements, or that you need a number to describe such a set in the first place. As a result, most numeral systems from history (eg. Roman numerals) don't contain a symbol for zero, or any way to represent the concept. The most 'natural' way to count is by making a mark for every item counted.

However ...... in the Netherlands (for example) it's generally taught that the natural numbers are {0, 1, 2, ...}.

So probably the best thing to do is avoid the term 'natural' altogether and use the term 'positive' or 'non-negative' to specify unambiguously which set you're referring to in any given context.

So, as I set from the go get, the definition of N* is best got from the teacher that is using it.
• Jul 4th 2009, 02:22 PM
skeeter