What is Domain: Definition and 741 Discussions

A domain name is an identification string that defines a realm of administrative autonomy, authority or control within the Internet. Domain names are used in various networking contexts and for application-specific naming and addressing purposes. In general, a domain name identifies a network domain, or it represents an Internet Protocol (IP) resource, such as a personal computer used to access the Internet, a server computer hosting a website, or the web site itself or any other service communicated via the Internet. In 2017, 330.6 million domain names had been registered.Domain names are formed by the rules and procedures of the Domain Name System (DNS). Any name registered in the DNS is a domain name. Domain names are organized in subordinate levels (subdomains) of the DNS root domain, which is nameless. The first-level set of domain names are the top-level domains (TLDs), including the generic top-level domains (gTLDs), such as the prominent domains com, info, net, edu, and org, and the country code top-level domains (ccTLDs). Below these top-level domains in the DNS hierarchy are the second-level and third-level domain names that are typically open for reservation by end-users who wish to connect local area networks to the Internet, create other publicly accessible Internet resources or run web sites.
The registration of these domain names is usually administered by domain name registrars who sell their services to the public.
A fully qualified domain name (FQDN) is a domain name that is completely specified with all labels in the hierarchy of the DNS, having no parts omitted. Traditionally a FQDN ends in a dot (.) to denote the top of the DNS tree. Labels in the Domain Name System are case-insensitive, and may therefore be written in any desired capitalization method, but most commonly domain names are written in lowercase in technical contexts.

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  1. N

    Domain of a Function | Open or Closed Interval?

    Homework Statement Hi If I have a function defined in one point only given by e.g. f(x) = 2, then is the function f defined on a open "interval" or a closed "interval"?
  2. C

    Self-adjointness domain of P_r^2

    hi everybody, i'd like to discuss with you a problem occurred to me in the study of a central symmetry field in non rel. qm. at a certain point, i get the linear operator P_{r}^{2}=\frac{1}{r}\frac{\partial^{2}}{\partial r^{2}}r , which is the square of radial momentum, and i want to determine...
  3. J

    What is the domain of validity of inverse square laws of Newton and coulomb?

    ¿what is the domain of validity of inverse square laws of Newton and coulomb? I think (correct me if this is false) that at the small scale these laws have been verified accurately , but ¿what happens with large distances? :rolleyes: . ¿Have been done an experiment which measured the...
  4. M

    Functions attaining max value => domain compact

    Homework Statement Prove that if every continuous real-valued function on a set X attains a maximum value, then X must be compact.Homework Equations None really.The Attempt at a Solution None really, not sure where to start. I know that if a space is compact, every function attains it's minimum...
  5. W

    F: [0,infinity) -> R is continuous at every point of its domain

    Problem: Assume that f: [0,infinity) -> R is continuous at every point of its domain. Show that if there exists a b>0 so that f is uniformly continuous on the set [b,infinity) then f is uniformly continuous on [0,infinity). I don't really know where to start with this one, any help would...
  6. S

    What is the domain of the given function when expressed in terms of x and y?

    Homework Statement What is the domain of the following function? f(x,y) = (\sqrt(x) + x\sqrt(y)) \sum_{k=1}^{\infinity} (k^3 + k) x^k y^k when D_f \subset \Re^2 . The Attempt at a Solution The domain is x>0 \in \Re and y>0 \in \Re in my opinion.
  7. N

    What is the domain of tan(x/b)?

    Homework Statement What is the domain for tan(x/b)? Homework Equations The Attempt at a Solution tan(x) domain is all real number , except x=\pi/2+n pi nEI tan(x/b)will be bpi/2+bnpi? Is there any form i can write? Am i right? Thanks
  8. H

    Find Absolute Max/Min for Function with Domain.

    [b]1. Find absolute max/min for the given function with the specified domain. f(x,y)= x^2-xy+y^2 on the circular disk x^2+y^2 less/equal 4, use parametrization when checking boundary. [b]2. f(x,y)= x^2-xy+y^2 x^2+y^2 less/equal 4 [b]3. The only thing I...
  9. S

    How to properly find the Domain of fog/gof ?

    Homework Statement f(x) = x + 1 D=[-9, 9] g(x) = x2 D=(1, 5) Question to be solved Find both g o f and f o g and specify their domains The attempt at a solution g o f = (x+1)2 This is where I don't really know what to do, however I'll let the logical part of my brain go a bit...
  10. r-soy

    I face some difficulties to find the domain

    I face some difficulties to find the domain Now i put my questions and please help me to answer it i try solve it thanks
  11. C

    Finding the Range of the Function f(x)=x²+4: Interval Notation Explanation

    Find the range of the equation. f(x)=x²+4Things I know for sure: x²>=0 We are brushing up on functions and interval notation in my calc class, and I can't remember how to do this in interval notation. If x is a number being squared it has to be positive or zero. So at the minimum the answer is...
  12. S

    Finding the Domain of the Bessel Function Series

    Homework Statement Find domain of \sum_{n= 0}^\infty \frac{(-1)^{n}x^{2n}}{2^{2n}(n!)^{2}} Homework Equations The Attempt at a Solution I set it all up but I can't really seem to simplify it. \frac{(-1)^{n+1}x^{2(n+1)}}{2^{2n+2}(n+1)!^{2}}\bullet\frac{2^{2n}(n!)^{2}}{(-1)^{n}x^{2n}}
  13. P

    What is the domain of f(g(x)) given f(x)= radical 25-x^2 and g(x)= ln(x+3)?

    1. Find the domain of f(g(x)) where f(x)= radical 25-x^2 and g(x)= ln(x+3) 2. For the domain of f I got x < or equal to +/- 5 and for the domain of ln(x+3) I got x+3 > 0 3. (0, 145) Thanks for your time. :P
  14. D

    Consider a simple function with a domain

    Homework Statement f(x) = e^{x}cos(x) has the domain [0, 2*pi] (a) Find the absolute maximum and minimum values of f(x). (b) Find the intervals on which f is increasing. (c) Find the x-coordinate for each point of inflection of the graph of f. No calculator use allowed. Homework...
  15. Z

    Domain of the composition of these functions

    Homework Statement Form the composition f o g o h and give the domain. f(x) = x - 1, g(x) = 4x, h(x) = x2 Homework Equations The Attempt at a Solution f(g(h(x))) = 4x2-1 The domain of x is any real number.
  16. S

    Parabolas: Domain, Range, and Completing the Square

    Homework Statement For the following questions, find the Domain and Range. Use either the graph or turning point method. Homework Equations 1. y= -x+6x-8 2. y= x^2-3x-5 3. y= -x^2+4x+4 And a question on the matter, when you complete the square, as in when I half the middle term...
  17. J

    Continuity and Domain of Function

    My question is best stated by using an example: Suppose f is a function defined only for rational x, and for rational x f(x) = 1. Say we want to prove that f is continuous at x = 1. Then we want to show that for every positive epsilon there exists a delta > 0 such that |f(x) - f(1)| <...
  18. M

    Conservative field over a domain

    Homework Statement prove that: \vec{F} = \frac{-y^2}{(x-y)^2}\vec{i} + \frac{x^2}{(x-y)^2}\vec{j} is a conservative field, and find the potential in the domain: D: (x+5)^2 + y^2 \leq 9 Homework Equations ? The Attempt at a Solution Well, \frac{\partial P}{\partial y} =...
  19. S

    Solving Laplace's equation over a triangular domain.

    When solving Laplace's equation over a triangular domain. Why is it a good idea to take M = N?
  20. M

    Finding Domain and Range of Functions

    Find the domain and range of y=sin^2x I have a hard type computing this into my graphing calculator. Can someone help in the steps to find the domain?
  21. S

    Sketch the domain where it is analytic

    Homework Statement determine if a) f(z) = e^z / (z^2 + 4) b) f(z) = conj(z) / |z|^2 c) f(z) = sum from 0 to inf. [ (e^z / 3^n) * (2z - 4)^n ] is analytic and sketch the domain where it is analytic. Homework Equations The Attempt at a Solution a) i don't know how to separate the...
  22. L

    Natural Domain of trig functions

    Homework Statement Find all the natural domain of the function algebraically, and confirm that your result is consistent with the graph produced by your graphing utility. h(x) = 3/2-cosx Homework Equations (a) h(x) = 3/2-cosx (b)x2-1/(x+1) The Attempt at a Solution Do I need to...
  23. M

    Domain of a Function with Sign Graph

    Homework Statement Find the domain of the function. You will need a sign graph. Answer in interval notation. Homework Equations f(x)= (3)/[(x2-4x)1/2] The Attempt at a Solution No clue - I don't know how to use a sign graph or what the positive/negative results mean as solutions on a number line.
  24. K

    What is the Domain of f(x) = x + 1? Exploring a Math Problem

    Suppose you have f(x) = ( x^2 + 4x + 3 ) / (x+3), making a scan in that function you can say that D : R / x =! -3, because x with -3 would give a division by zero. But, suppose you simplify that function by factorizing, you get f(x) = x + 1 It would represent the same value, but my teacher...
  25. M

    What Values of (x, y) Make f(x, y) = 1/(x - y^2) Undefined?

    Here is my question, that what is the domain of f, while f(x,y)=1/(x-y2)
  26. J

    Composition of functions, domain, range

    A = (0, infinity), B = C = D = R where R is all real numbers f: A->B, g: B->C, h: C->D f(x) = lnx, g(y) = 3y, h(z) = e^z h o g o f ? -------------------------------------------- For the following to be defined doesn't 1) range(f) ⊆ domain(g) 2) range(g o f) ⊆ domain(h) So g o f should be...
  27. J

    Composition of functions and being defined thru range and domain

    For the following to be defined doesn't 1) range(f) ⊆ domain(g) 2) range(g) ⊆ domain(h) Is that correct? So R ⊆ R for 1, and R ⊆ R for the other so it is ok? --- Second question: but how can you have the function h with the range of all real numbers when the exponential function only has a...
  28. C

    Finding the domain of an equation

    Homework Statement Find the Domain of f f(x)=2+7x (2+7x is in square root) Homework Equations The Attempt at a Solution I'm really not sure. The possible answers i think of seem far to easy. This problem's annoying me because i remember doing it in alg. 2 but it was so long...
  29. T

    Integration over an Ellipsoidal Domain - Clarification

    Homework Statement I want to integrate a function over an Ellipsoidal domain. \[...
  30. A

    What is the Difference Between a Vector Space and a Coordinate Space?

    Say we have a function, f(x)=x^3 one would say "f is a function from \mathbb{R} to \mathbb{R}" or f: \mathbb{R}\to\mathbb{R} Then say we have a vector function, \vec{g}(t)=<t^2+1,t> . How would one use the above notation? Would it be \vec{g}: \mathbb{R}\to\mathbb{R}^2 ? And...
  31. L

    Finite Difference Frequency Domain

    Hello everybody! I am trying to construct the FDFD method for 3D structures. I have already constructed the general formulation and specifically I have set the complete matrix form. Due to the fact that the matrices are too sparse, and my system is out of memory, I am trying to set the problem...
  32. S

    A very basic question: can the null set be the domain of a function?

    In other words, is the domain of a function by definition non-empty? (If I define a function from A to B should I take care to ensure that A is non-empty?)
  33. H

    Prove that the group ring Z p G is not a domain.

    Prove that the group ring ZpG is not a domain. Homework Statement Let G be a finite group and let p >= 3 be a prime such that p | |G|. Prove that the group ring ZpG is not a domain. Hint: Think about the value of (g − 1)p in ZpG where g in G and where 1 = e in G is the identity element of...
  34. Z

    Using time to define space domain

    So I created this storage container object for a program I need to write for C++. In applying my way to store data in a single 2dimensional array I came across a weird connection, and after trying to connect the dots I find myself trying to represent what I can only describe as the domain...
  35. K

    Indefinite Integrals in the Complex domain

    Homework Statement I'm looking at integrals about the unit circle and need to show that they equal 0. integral[e^zdz/(z-2)] integral(sinz/zdz) integral[sinhz/(z^2+2z+2)dz] My thoughts on showing these is using series. Is this the right idea? Also I'm looking at a couple of...
  36. J

    If a function f is differentiable at a point x = c of its domain, then

    If a function f is differentiable at a point x = c of its domain, then must it also be differentiable in some neighborhood of x = c?
  37. S

    Domain of influence for wave equation in 2 dimensions

    Hello, I have some trouble seeing why the solution of the wave equation in 2 dimensions exist at all later times once it passes an initial disturbance... For example, take a simple case where the initial position is zero, and the initial velocity equals some function inside some circle domain...
  38. J

    Proving Invariance of Domain Theorem

    Hello, For spring break homework, I'm supposed to prove the Invariance of domain theorem (stating that continuous injective functions from an open set in R^n to R^n are open maps). Does anyone know of any books/sources of any kind which will help? Thanks!
  39. X

    Restricting Domain and Range in broken conics

    Homework Statement How do you know whether you restrict the domain or range with a horizontal ellipse ? Homework Equations x^2/49 +y^2/10=1 The Attempt at a Solution
  40. J

    What Are the Domain, Image, and Codomain of f(x) = 1/x?

    1. Let f(x)= 1/x where x is a rational number. What is the domain of f? Give a codomain and image for f that are not equal to each other. I am not sure about my answers, I got: D= (-infinity, 0) U (0, infinity) Image= (o, infinity) Codomain= Set of all reals I don't think this is...
  41. C

    Understanding Domain & Range in R^2: Conditions for Image in Boundary

    Can you help me with this? I have a function with domain and range in R^2. What conditions it must have so that a point in the boundary of the domain will have its image in the boundary of the range? Thanks.
  42. J

    Domain and range of the function help needed work shown

    domain and range of the function help needed.. work shown! Given the function f(x)= (3x+4)/(5-2x) find the domain and range of the inverse function of f(x) work shown: it was proven to be one to one since f(x1)= f(x2) found inverse f(x) to be (5x-4)/(3+2x), i believe this is correct...
  43. D

    What is the natural domain and range for f(x,y) = 1/sqrt(x^2-y)?

    define the natural domain and range for f(x,y) = 1/sqrt(x^2-y) I get D= {(x,y)|x^2-y>0} same as saying y can not equal x^2 R= {(x,Y)|f>0} can someone tell me if I've approached this correctly?
  44. W

    1D COMSOL Domain Implementation

    Hello, This is the first time I'm using COMSOL on a problem where I have multiple subdomains within the domain. Previously, I have only been using one domain/one set of equations/Two global sets of BC's. I've been having a hard time thinking of a solution to my problem. I have 3...
  45. P

    Cramer's Rule in Complex Frequency Domain.

    Does Cramer's rule work in frequency domain? For example, if we have to solve two simeltaneous equations, as in nodel analysis or mesh-current method, can we use Cramer's rule to solve em? Would this be an efficient method?
  46. G

    Domain of g(x): [-1,2) | Calc Homework Question

    Homework Statement I have a review in Calc and the question was: f(x) has a domain of [-1 , 5) Find the domain of g(x) = f(2x+3) Homework Equations The Attempt at a Solution I got [-1 , 2)
  47. M

    Find domain of f(x)=x^(5/3)-5x^(2/3)

    f(x)= x^(5/3) - 5x^(2/3) Need to find the domain of the above function? The graphing calculator shows x cannot be a negative number, and I don't see why not? Please help!
  48. C

    How Do You Convert a Time Domain Waveform to Frequency Domain in MATLAB?

    Homework Statement Dear all , Am new to matalb and am having some couple of problems. i want to convert the following wave form from time to frequency domain . 1.E=ACos(ωt+φ).[0,T] I have made conversion by using integration by parts.Please find the MATLAB attached files...
  49. E

    Slope-intercept, (determine, evaluate, domain) function, diff. quotient

    Domain Functions: f(x) = 4sq.root(1-x2), the 4 is on the outside f(s) = sq.root(s -1)/s-4 f(x) = x-4/sq.root x I have absolutely no clue how to go about doing any of these, I take notes but I cannot piece it together; I have never felt so helpless at anything. This isn't homework I...
  50. N

    Images in the frequency domain

    Hi, I've been trying to understand more on frequency plots of images. 1. Assuming a 1d example of just a strip of an image; in the frequency map there are 'same' no. of frequencies as there are pixels. What is the reason for this? Does this have something to do with the Nyquist theorom...
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