Domain is what goes in, range is what comes out. Domain is x, range is y. Domain is left to right, range is bottom to top! Have an example of where you're confused? Answer from matt7259 on reddit.com
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IntMath
intmath.com › home › introduction to geometry › 4a. domain and range of a function
Domain and Range of a Function
Simple explanation for domain and range. We learn the domain of a function is the set of possible x-values and the range is the resulting set of y-values.
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Domain and Range for a function f(x)
Change f(x) to y and it should work More on reddit.com
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Can someone please explain Domain and Range? : learnmath
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[College Trig] Domain and range of trig functions

No, it doesn't change the domain of the trig function. You are given an interval to graph because you can't possibly graph the entire domain. As you said for sine, it can go on forever in either direction.

But let's clarify that one: the reason that the domain of sine is all real numbers is not exactly because it can go on forever. It is all real numbers because you can substitute any and and all real numbers for x into the function y=sin(x) and get a real number output for y.

If you look at the graph of y=tan(x), it also "goes on forever in either direction" BUT it has discontinuities at regular intervals. This is because tan(x) is undefined for the x values pi/2 + n*pi where n is an integer, causing vertical asymptotes at those x values. Since there is no real number output for y for those x values, they are excluded from the domain.

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determine the domain and range of the trig function

Start with the domain and range of f(a) = cot(a) and work your way to the answer.

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Purplemath
purplemath.com › modules › fcns2.htm
The Domain and Range of Functions
A function's domain is where the function lives, where it starts from; its range is where it travels, where it goes to. Just like the old cowboy song!
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Mathematics LibreTexts
math.libretexts.org › bookshelves › applied mathematics › calculus for business and social sciences corequisite workbook (dominguez, martinez, and saykali) › 4: functions
4.7: Domain and Range of a Function - Mathematics LibreTexts
July 18, 2022 - The domain of a function is all possible values of x that can be used as input to the function, which will result in a real number as the output. The range of a function is the set of all possible …
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Math is Fun
mathsisfun.com › sets › domain-range-codomain.html
Domain, Range and Codomain
In its simplest form the domain is all the values that go into a function, and the range is all the values that come out.
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Mathway
mathway.com › Calculator › domain-range-calculator
Domain and Range Calculator | Mathway
The Domain and Range Calculator finds all possible x and y values for a given function.
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Cuemath
cuemath.com › calculus › domain-and-range-of-a-function
Domain and Range - From Graph | How to Find Domain and Range of a Function?
The domain and range of a function are the components of a function. The domain is the set of all the input values of a function and the range is the possible output given by the function. Domain→ Function →Range.
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GeeksforGeeks
geeksforgeeks.org › mathematics › domain-and-range-of-function
Domain and Range | How to Find Domain and Range of a Function - GeeksforGeeks
... A quadratic function is a polynomial function with degree 2 i.e. f(x): ax2 + bx = c = 0 is a Quadratic Function. Example: For g(x) = x2 − 4, the domain is all real numbers, but the range is restricted.
Published   October 11, 2022
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Study.com
study.com › math › algebra
Domain & Range of a Function | Definition, Equation & Examples - Lesson | Study.com
January 11, 2013 - The range of a function is the set of all output values in which the function is defined. Or, in another way, it is the set of all values that the function takes. ... The input values appear in the x column while the output values appear in ...
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Varsity Tutors
varsitytutors.com › home › domain and range
Domain and Range
The domain of a function is the set of all values for which the function is defined, and the range is the set of all values that the function takes.
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YouTube
youtube.com › tabletclass math
Understand Domain and Range - YouTube
Understand the domain and range of a function. The domain is the set of all values that can be input into a function and the respective output values are the...
Published   July 5, 2018
Views   490K
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Appspot
precalculus.appspot.com › RelationsFunctions › domainRange.html
Domain and Range of Functions
This means that any result we have, would be multiplied by $-1$ That makes all our results to be nonpositive (zero and negative numbers only). $ R = \{y | y \le 0\} \\[3ex] R = (-\infty, 0] $ ... It is an absolute value function. It is not a one-to-one function. Two input values can have the same output value. To find the domain, we have to consider the range of numbers that can be inside the absolute value which would give a result, and see if that result added to $7$ would give a result.
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Mometrix
mometrix.com › home › how to find domain and range
How to Find Domain and Range (Video & Practice Questions)
October 21, 2025 - The domain is any number we can put in place of the \(x\). You could put 1, 2, -7, 84, or any other number in place of the \(x\). This means that the domain is: \(-\infty\leq x\leq\infty\). Another way to say this is that the domain is the set of all real numbers. What about our range? Well, if I plug in 1 for \(x\), I get 7 and if I plug in 2 for \(x\), I get 11.
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IXL
ixl.com › math › algebra-1 › domain-and-range-of-relations
IXL - Domain and range of relations (Algebra 1 practice)
Improve your math knowledge with free questions in "Domain and range of relations" and thousands of other math skills.
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Wikipedia
en.wikipedia.org › wiki › Function_(mathematics)
Function (mathematics) - Wikipedia
2 weeks ago - A specific element x of X is a ... or the image of x under the function. The image of a function, sometimes called its range, is the set of the images of all elements in the domain....
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GeeksforGeeks
geeksforgeeks.org › mathematics › introduction-to-domain-and-range-relations-and-functions
Domain and Range of a Relation - Definition, Types, and Examples - GeeksforGeeks
The domain is the set of all possible input values (the "x" values), and the range is the set of all possible output values (the "y" values) in a relation.
Published   October 6, 2025
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BYJUS
byjus.com › maths › domain-codomain-range-functions
Domain Range and Codomain Of A Function
August 17, 2022 - ... The set of all the outputs of a function is known as the range of the function or after substituting the domain, the entire set of all values possible as outcomes of the dependent variable.