Question about inverse functions

In summary, if F(g(X))=X has been proven, it is necessary to also prove g(f(X))=X to confirm inverse functions. However, there can be cases where the first statement is true but the second is false, as not all inverse functions are themselves functions. For example, if f(x)= x^2 and g(x)= \sqrt{x}, f(g(x))=x but g(f(x))=|x|, unless the domain of f is restricted to non-negative numbers.
  • #1
Spirochete
127
0
If you've already found that F(g(X))=X, is it necessarry to also prove that g(f(X))=X to know that you have inverse functions? Would there be a case where the first statement is true but the second is false?
 
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  • #2
Spirochete said:
If you've already found that F(g(X))=X, is it necessarry to also prove that g(f(X))=X to know that you have inverse functions? Would there be a case where the first statement is true but the second is false?
The inverse of many functions are not functions themselves.
 
  • #3
In particular, if [itex]f(x)= x^2[/itex]] and [itex]g(x)= \sqrt{x}[/itex], [itex]f(g(x))= (\sqrt(x))^2= x[/itex] but [itex]g(f(x))= \sqrt{x^2}= |x|[/itex]. Of course, if the domain of f is restricted to the non-negative numbers, then they are inverses.
 

1. What is an inverse function?

An inverse function is a function that undoes the action of another function. In other words, if a function f(x) takes an input x and produces an output y, then the inverse function f^-1(y) takes the output y and produces the input x.

2. How do you find the inverse of a function?

To find the inverse of a function, you need to switch the input and output variables and solve for the new output variable. For example, if the original function is f(x) = 2x + 3, the inverse function will be f^-1(x) = (x - 3)/2.

3. Are all functions invertible?

No, not all functions are invertible. A function must be one-to-one (each input has a unique output) in order to have an inverse. If a function is not one-to-one, it is not possible to reverse the action of the function.

4. Can a function have more than one inverse?

No, a function can only have one inverse. This is because the inverse function must also be one-to-one, and if there are multiple outputs for a single input, it is not a function.

5. Why are inverse functions useful?

Inverse functions are useful because they allow us to "undo" the action of a function. They can help us solve equations, find missing input values, and understand the relationship between input and output variables in a function.

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