What does this mean? Looks like (X E R) and please help!!!?

Theres a sign that looks something like X E R.. capital E but smaller.. my teacher said it's a replacement for "Set of real numbers" but is that right? I wrote it with paint as well because i couldnt find symbols..

Here's the link you have to put it together:















Also if this does mean "Set of real numbers" how is that the domain and range of a circle? Circles are not like a line which goes on and on.. infinite o.O

4 Answers

  • lol, no way am I putting that thing together, just paste the link. We can click them.

    xeR is likely : x ∈ ℝ

    "x is in the set of real numbers"

    ∈ = "in" or "is an element of"

    ℝ = real number set

    It tells you what values x can take on. Examples may help, if we had

    ℤ = integer set = {..., -4, -3, -2, -1, 0, 1, 2, 3, 4, ....}

    ℂ = complex number set

    ℚ = rational numbers (numbers that can be represented as a fraction with the numerator and denominator both being integers)

    ℕ = natural number set = {1, 2, 3, 4, 5, ....} (sometimes people say it includes zero too)

    Note, you can even use these symbols to further define some of the larger sets:

    ℚ = {p/q : p ∈ ℤ, q ∈ ℕ}, which is a statement of both the numerator and denominator being integers, and specifying that q cannot be zero (cannot divide by zero)

    ℂ = {a + b i : a,b ∈ ℝ}

    If we say

    (1) x∈ℤ, x could be 1, or -53 or 100000, or whatever, so long as it is an integer

    (2) x∈ℚ, x could be 1/2, or 324242 / 4321804923, or anything, but it could not be for example 3.141592654....= pi, since you cannot write pi as a fraction with whole numbers

    (3) x∈ℕ, if we say ℕ is {1, 2, 3, 4, ....}, then x could be 1, or 43908, or 239043248, but not for example -3, because it is not in the set

    *****(4) x∈ℝ, x could be any number on the number line, this is the largest set for real numbers (since it is all real numbers). x could be 3280492, or 0.32894382, oro 48389.3242, or -384209482/32490289.3232, or even pi.

    It does not have anything to do with ranges, there is no function here. These specify domains (the values of what x can and cannot be). Circles and lines have to do with functions, which have ranges, and domains. Please review the definition of ranges and domains, and consult with your teacher to better understand it. I do not think it would help as much as if you were to receive the explanation in real life, with pictures, etc. There is only so much you can do in text.

  • Hello,

    The "E" is sort of a roundy capital "E", right?

    "X" means "any number".

    "E" means "is an Element of".

    "R" means "the set of Real numbers".

    For the domain and range...it depends on which function you use to draw the circle. Only functions have domain and range.

    If you use a polar function, which uses angle and radius instead of X and Y, you could draw a circle by saying "f(t)= rpit", where t is the angle. Then t (your domain) could be as big as you want, and f(t) (your range) would just go round and round and round, to infinity.

    So in a way...a circle IS a line which goes on and on.

  • D = {0, 1, 2, 3, 4, ...}, natural numbers with zero R = {1, 3, 5, 7, 9, ...} , odd numbers (Koherodin)

  • What Does Xer Mean

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