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. A

    Why can you do Convolution in frequency Domain?

    Hi everybody, I have question: Why can you do Convolution filter in the frequency Domain ? I mean, when you apply a filter to an image in the spatial domain, it 's easy. You've got for example your sobel 3x3 kernel that you apply on every pixel of your image. Easy. But when you convert...
  2. GRB 080319B

    Domain Wall Catastrophe: Is There Any Evidence?

    http://www.starstreamresearch.com/vacuum_reaction.htm" I know this sounds like a lot of crackpottery, especially near the end of the article, but is there any scientific evidence in support of something like this happening?
  3. L

    What is a Schlicht Domain in Complex Analysis?

    Whatever is a schlicht domain (complex analysis)? Laura
  4. DaveC426913

    Is my domain on AOL's blacklist and how can I fix it?

    I've just discovered why my emails are bouncing back from particular friends. Those friends have AIM accounts (or similar), and it seems AOL (or other) has blacklisted my domain. A few months back my site was hacked and someone was using it for phishing. With the help of my ISP I've deleted...
  5. A

    Engineering RLC circuit step response time domain

    This is more of a math question but i feel like i will get more help among Electrical Engineers. I successfully found the step response of an RC circuit in the time domain using Laplace Transforms. But i can't seem to figure out how to do it with an RLC transfer function. I have the following...
  6. L

    Def'n of holomorphically convex domain

    Does anyone have a textbook on multivariable complex analysis, and do they define a holomorphically convex domain in terms of the union of an ascending series of compact subsets? If so, how exactly does the definition go? Was it D=\bigcup K_n where K_n is holomorphically convex and compact...
  7. F

    Proving Integral Domain of D Using Commutative Ring

    Homework Statement Given a,b,c in D, with a not 0, we have ab=ac implies b=c. Show that the commutative ring D is an integral domain. The Attempt at a Solution I don't know where to begin with this.
  8. F

    !AC Generator Current: Mathematical Expression in Time Domain

    Consider a simple alternating current generator such as Hippolyte Pixii's dynamo. The current generated by such dynamo can be described as simple oscillating cosine signal. Assuming for simplicity that the max current generated each time a pole of Pixii's magnet passed the coil is (2/pi)0.5...
  9. C

    Time Domain Functions to Frequency Domain

    How do you convert functions from the time domain, to the frequency domain For example: cos(250t + 30degrees) is what in the frequency domain? Are there some general steps I can follow to do this?
  10. L

    Empty Relations: Domain, Range & Functionality

    What is an empty relation? Can an empty relation be a function? Is an empty relation one with the empty set as its domain or as its range or both? THanks
  11. R

    Domain and range of functions of 2 variables

    I'm doing some exam revision and there's a few questions on finding the domain and range of functions of 2 variables. With a function of 1 variable I know that the domain and range is just finding the max and min x value, and the max and min y value. With a function of 2 variables I am...
  12. S

    Proving Nonempty Fibers of a Map Partition the Domain

    Homework Statement Prove that the nonempty fibers of a map form a partition of the domain. The Attempt at a Solution Ok so we have some map phi: S -->T And we want to show that its pre-image phi-1(t) = {s in S | phi(s)=t} forms a partition of the domain. Im really confused here. I assume...
  13. P

    Proving R is Not a Domain: A Counterexample Approach

    Homework Statement Show that R = {0.5(a+b(root2)) : a,b are integers} is not a domain [b]2. Homework Equations A commutative ring (non trivial) is a domain iff (ab=0 => a=0 or b=0) The Attempt at a Solution I've try to construct a counterexample where x, y in R and xy=0 but x,y=/=0...
  14. D

    Domain and range in ovals-what's this called?

    Domain and range in ovals--what's this called? I was helping my friend with his math homework. He's in an intermediate algebra and is working on domains and ranges of functions. He came to me for help with this method of describing domains and ranges of functions using two ovals--one listing...
  15. A

    Is My Understanding of Domain Notation Correct?

    I just have a question which I'm confused about, this is the same right? Domain is (-∞,0) U (0,+∞) and Domain D: {XER, x ≠ 0} and this is the same right? Domain is (-∞,0) U (5,+∞) and Domain D: {XER, x ≠ 0, x≠ 5} Attempt : I know that U is used to...
  16. X

    Finding Domain of f(x) & g(x) Equations

    Homework Statement Find a. (f+g)(x) b. (f-g)(x) c. (fg)(x) d. (f/g)(x) f(x)=2x-5 & g(x)=4 Homework Equations (f+g)(x)=2x-1 (f-g)(x)=2x-9 (fg)(x)=8x-20 (f/g)(x)=2x-5/4 The Attempt at a Solution When I've completed all the other equations, I'm stuck on domain. I'm thinking that its all...
  17. K

    Find the domain of the function

    hi this is my first time here. i have just been admitted to the university of the gambia last month. i have a problem with this question. please i need help find the domain f is such that x maps to 1 all over the squareroot of x2-10x+12.
  18. P

    Domain and image of a function

    We recall that Z is the set of all integers. For each i, j in Z, let f(i,j) be the larger of the two integers i and j. Do these remarks define a function? If so, what are the domain and the image? I'm not sure how to do this. I believe that the remarks do define the function. But I don't know...
  19. P

    A simple domain not being skew field?

    Can you find an example of a simple domain not being skew field?
  20. L

    Why is the domain of arctan power series |x|<=1?

    Why is the domain of arctan power series |x|<=1? i understand why a power series has the domain |x|<1, but why is the power series of arctan |x|<=1? thanks! also, why are domains of the taylor expansions of coshx and sinhx: for all x?
  21. F

    Write down the domain and range of the function

    Write down the domain and range of the function g(x) = 1 / ((9 - x)2) Please enter your answer as a list [in brackets], using inequalities e.g. a domain (for x) of (-¥, 2) and a range (for g(x)) of (2, 5] may be entered as: [x < 2, 2 < g(x) and g(x) <= 5] I don't get it??
  22. S

    Why Should x=0 Be in the Domain of y?

    Homework Statement y= \frac{x + \frac{1}{x}+1}{x+\frac{1}{x}+2} That is equal to y = \frac{x^2+x+1}{(x+1)^2} Whenever I graph either one of those they are the same graph (as well they should be) and they have a value for x=0. But why should x = 0 be in the domain? And also if you go...
  23. H

    Drawing the Domain for Double Integral of Function of Two Variable

    This is not for a specific problem, just in general: If we want to find the double integral of a function of two varaible, when we got other 1 varaible function to define the domain. What are the basics of drawing the domain in 2d (x, y only)?
  24. N

    Domain & Range of f: Identifying Math Function

    Identify the domain and range for the function f= {(x,y) \in \mathbb{R} x \mathbb{R}:y=\chi _{\mathbb{Z}}(x)} f={(x,y)\in \mathbb{R} x \mathbb{R}:y=\frac{e^x + e^{-x}}{2} How do I determine the correct results. I am not really understanding the terminology.
  25. S

    What is the domain and range of y = 1/(x-1)(x+2)?

    Homework Statement y = \frac{1}{(x-1)(x+2)} find out the domain and range ans: y<= -4/9 or y>0 x~E~R~-\{-2,1\} The Attempt at a Solution I know the solution and I used this methoD: y(x^2 + x -2) =1 (where y\neq0 ) when x is real, the discriminant y^2...
  26. B

    State the domain of the function and the domain of its derivative

    Find the derivative. State the domain of the function and the domain of its derivative. f(x) = x + √x f(x) = (3 + x) / 1-3x Find F'(a) f(x) = (x^2 + 1) / (x - 2) f(x) = √3x + 1
  27. quasar987

    Other names for the domain and range-straightening theorems?

    I'm trying to find the wiki page (if it exists) on the domain-straightening theorem and the range-straightening theorem but searches for those words produce no results. I've also seen those theorems by the name of "canonical forms for submersion and immersion" (in Gallot-Lafontaine-Hullin)...
  28. D

    Integrate on a triangular domain

    Hi! I have to integrate on a triangular domain \int_T f(x,y,z)dxdydz so I use simplex coordinates, i.e. x=(1-\alpha-\beta)x_1+\alpha x_2+\beta x_3 y=(1-\alpha-\beta)y_1+\alpha y_2+\beta y_3 z=(1-\alpha-\beta)z_1+\alpha z_2+\beta z_3 where (x_i,y_i,z_i) are the vertices of...
  29. N

    The domain of a cartesian function from parametric equations

    x = 2cot t y = (sin t)^2 t is greater than 0 but less than or equal to pi/2 The cartesian can be found using trig identities to be: y = 8/ (4+ x^2) What would be the range of the cartesian equation? I think it would be x is greater than or equal to 0, since when t = pi/2, x =...
  30. N

    What is the domain of the inverse function for f(x) = ln(4 - 2x)?

    The function f is defined by f(x) = ln(4 - 2x), x<2, and x is a real number write down the domain of the inverse. I know that the domain of the inverse is the range of the function, but I am puzzled as to what that would be! Would it just be any real number? Thanks
  31. J

    Translating integration domain

    If f:\mathbb{R}^3\to\mathbb{R} is a continuous function, x_0\in\mathbb{R}^3 a fixed point, r>0 a fixed radius, and n\in\mathbb{R}^3 a fixed vector satisfying |n|=1, then is the equation \int\limits_{B(x_0 + \alpha n, r)} d^3x\; f(x) \;=\; \int\limits_{B(x_0, r)} d^3x\; f(x) \;+\...
  32. L

    Fortran Error: Run-time error M6201-MATH -atan2: Domain Error

    Hi All, I have some problem about my Fortran program. When I execute my program, it says Run-time error M6201-MATH -atan2 : Domain error I don’t know what to do. Please help me out from this error. Thanks Logi
  33. X

    Understanding the Cosine Wave Frequency Domain

    So...a cosine wave when shown in the frequency domain is represented by a 1/2 magnitude vector at the positive frequency and a 1/2 magnitude vector at the negative frequency. I am surprised by this because I cannot understand why a vector of magnitude 1 at the positive frequency of the cosine...
  34. L

    How do you set up an integral integrating two functions within a domain?

    How do you set up an integral integrating two functions within a domain?? Homework Statement I have to integrate (2 + x + y) within the domain that is the area between 0 and 1 and (x+y<=1) I know how to integrate well, I think it's a double integral but I'm not really sure what the range...
  35. O

    Domain and range of this function?

    Homework Statement (1/(x+7))-5 find the domain and range. im having trouble graphing this one on my calculator, because when i zoom out the graph looks a lot different than when i zoom in. i think i have an answer though, so i need a quick check. domain: none (infinite) rangE: 0 to -10?
  36. A

    Chemistry Electron Domain Geometry vs Molecular Shape

    What's the difference between "Electron Domain Geometry" and "Molecular Shape"? Please help! Thanks
  37. A

    Domain of g(x) = (x-2)/(x^2-9) |x|≠3

    for g(x) = (x-2) / (x^2 -9) the domain of the function would be simply to have the denominator not equal to 0, which in this case would be x = 3. but.. the solution states that it is -3 and 3 cannot be used. this is confusing seeing that -3^2 -9 = -18 which is not 0. maybe it...
  38. N

    Numerical PDE's II - Circular Domain

    Homework Statement Approximate the solution of: \frac{\partial^{2}u }{{\partial r^{2} }} + \frac{1}{r}\frac{\partial u}{\partial r} + \frac{1}{r^{2}}\frac{\partial^{2}u}{\partial \theta^{2}} = 0, 1<r<3, 0<\theta<\pi, u(1,\theta) = 1-\cos(\theta),u(2,\theta)=u(r,0)=0 u(r,\pi)=4-2r...
  39. C

    Domain of y=sqrt(cosx): 1st & 4th Quadrant of Unit Circle

    What would the domain of y = sqrt(cosx) be in mathematical terms. I know that it is all the reals that lie in the first and fourth quadrant of the unit circle, but how would you express that in mathematical terms?
  40. A

    Laplace domain to time domain

    i have a question about laplace transforms. I had to find the maximum of a three exponential equation f(t). What I have done is took the first derivative of f(t) and equated it to zero. Now f'(t) is also a three exponential equation ( like f'(t)= e^at +e^bt +e^ct). So I have taken laplace...
  41. A

    Laplace domain to time domain

    Homework Statement i have a question about laplace transforms. I had to find the maximum of a three exponential equation f(t). What I have done is took the first derivative of f(t) and equated it to zero. Now f'(t) is also a three exponential equation ( like f'(t)= e^at +e^bt +e^ct). So I...
  42. R

    Are the following functions? Give domain and range

    Homework Statement State if the following is a function. If yes, write domain and range. A. {(x,y): y=(x^1/2) ; x,y are real numbers and x>0} B. {(x,y): y^2=x ; x is real numbers and x>0} Homework Equations A relation is called function if each element of the domain...
  43. A

    Domain of a Differential Equation

    Find the particular solution y=f(x) to dy/dx=(1+y)/x given that f(-1)=1 and state its domain. My answer was: 2|x|-1, x ∈ ℝ/{0} Apparently, the domain should be x<0 Solving the differential equation was not an issue at all, but I have no idea why the domain is restricted to x<0. I...
  44. D

    Domain & Range Homework: Difference Explained

    Homework Statement I don't really know how to ask this, so I'll get straight into an example. x:x\in(-\infty,\infty) but x\neq1 x:x\in(-\infty,1)\cup(1,\infty) what is the difference between these two intervals? Homework Equations The Attempt at a Solution
  45. quasar987

    Exploring if 0 is a Prime Element in an Integral Domain

    [SOLVED] Is 0 a prime? Am I missing something or is 0 a prime element in an integral domain? In the definition of prime element p of an integral domain, we only ask that the ideal generated by p, be prime. Well (0) is obviously prime because if ab=0 in an integral domain, then it is that...
  46. T

    Is P(X<Y) Equal to 1/3 for f(x,y) = e^{-x-2y}?

    If f(x,y) = e^{-x-2y} find P(X<Y) . So is this equaled to 1 - P(X>Y) = 1 - \int\limits_{0}^{\infty} \int\limits_{0}^{x} e^{-x-2y} \ dy \ dx = \frac{1}{3}?
  47. I

    Understanding Domain Notation: Explaining 2<x<4 in Graphs and Equations

    Homework Statement I have to do a few graphs and some equations with certain domains but I've never seen the domain written in this way: Usually I see the domain written with something like 2<x<4. What exactly does the above mean?
  48. 1

    Domain & Range: Calculus Help, Graphs

    Calculus Help, Please. (Domain, Range, Graphs) Homework Statement Determine its domain and range. f(x) = {2x+1, x<0 {2x+2, x => 0 f(x) = {x^2 + 2, x<=1 {2x^2 + 2, x >1 f(x) = { |x| + 1, x<1 { -x +1, x=>1 Homework Equations No equations...
  49. N

    What Is an Alternative Domain for Sec(x)?

    Homework Statement A problem in my textbook gives the domain of sec x as [0,(pi/2)) U ((pi/2), pi]. This makes perfect sense of course. However, it is asking for an alternate domain. I've looked at the graphs of both sec x and arcsec x to try to figure out a different domain for sec x(I looked...
  50. G

    Domain of f(x) = (2x^2 + 25)^(0.5) + 1 - Help Needed

    I was wondering if there's any symbol i could use for the domain of this question f(x) = (2x^2 + 25)^(0.5) + 1 as we can see that , f(x) will always be greater or equal to zero , was wondering what would the domain be ? Could anyone help me out ? thanks
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