What is the difference between range and codomain in a function?

[danago]

Hi. This isn't directly a homework question, but it will help in general.

Im having a little trouble understanding what the difference between a range and codomain is. For example, for the function f(x) = \frac{3}{{2x - 2}}, i understand that the domain is \{ x \in R:x \ne 1\}. Now, i also believe that the possible values that can be outputted by the function is given by
<br /> \{ f(x) \in R:f(x) \ne 0\} <br />. Is this the codomain or range?

Thanks in advance,
Dan.

 

[dextercioby]

The range/codomain is the image of the domain through the function

\mbox{Ran}(f(x)):=\left\{ f(x)\left|\right x\in D(f(x)) \right\}

In your case, first make a plot of the function first.

 

[f(x)]

Hi. This isn't directly a homework question, but it will help in general.

Im having a little trouble understanding what the difference between a range and codomain is. For example, for the function f(x) = \frac{3}{{2x - 2}}, i understand that the domain is \{ x \in R:x \ne 1\}. Now, i also believe that the possible values that can be outputted by the function is given by
<br /> \{ f(x) \in R:f(x) \ne 0\} <br />. Is this the codomain or range?

Thanks in advance,
Dan.

that is the range of the function. codomain is usually a superset (sometimes equal as well) of the range. its generally defined in the question itself, like f:R-->R (here both domain and codomain are the set of real nos.),but range will be a subset(or an equal set) of R depending upon the function definition.

 

[HallsofIvy]

According to Wikipedia, the "codomain" of a function f:X-> Y is the set Y. The "range" is the subset of Y that f actually maps something onto.

For example, if f:R->R is defined by f(x)= e^x, then the "codomain" is R but the "range" is the set, R⁺, of all positive real numbers.

Notice that you cannot tell the "codomain" of a function just from its "formula". I could just as easily define f:R->R⁺, with f(x)= e^x. Now the codomain and domain would be the same.

 

[foxtrot_echo_]

Notice that you cannot tell the "codomain" of a function just from its "formula". I could just as easily define f:R->R⁺, with f(x)= e^x. Now the codomain and domain would be the same.

I have a doubt, I think we also cannot tell what the "domain" is just from the "formula" . We can say what it "is not" but we can't say what it "is".

for instance we can define a function as f:[1,2]->R , with f(x) = e^x . here "domain" is what we define(i.e [1,2]) ,"co-domain" is what we define(i.e R) , but "range" is obtained from the formula, which in this case would be [e,e^2]

but the formula definitely can tell us what domain is not.
ex :- f(x) = \sqrt{x} we can't say domain is R. we have to define domain as R^{+} or it's subsets.