Determining & Proving Inverse Functions: Methodology?

In summary, the conversation revolved around determining and proving whether or not a function has an inverse. One method suggested was by checking if the function is a bijection, which can also be done using the "horizontal line test". However, a follow-up question was raised about functions that are invertible but cannot be expressed in terms of elementary functions. The conversation did not provide a general method for proving this.
  • #1
jgens
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Does anyone know of an existing methodology for determining and proving whether or not a function has an inverse?

Thanks.
 
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  • #2
How about by determining if the function is a bijection? Or am I missing something here?
 
  • #3
The "horizontal line test". How many times does any horizontal line cross the graph of the function? Which is the same as "determining if the function is a bijection"!
 
  • #4
Thank you very much. Just a brief follow up question: Suppose a function is invertable but the inverse has no representation in terms of elementary functions (I'm including trigonometric and logarithmic functions in this category) - I think f(x) = x + sin(x) would meet this criterion - is there a general method for proving that the function does not have an inverse expressable in terms of elementary functions?

Sorry if that doesn't make sense.
 

1. What is the methodology for determining inverse functions?

The methodology for determining inverse functions involves a few key steps. First, you need to find the original function and rewrite it in terms of x and y. Then, swap the x and y variables and solve for y to get the inverse function. Finally, check the domain and range to ensure that the inverse function is indeed the inverse of the original function.

2. How do you prove that two functions are inverses of each other?

To prove that two functions are inverses of each other, you need to show that their composition results in the identity function, which is f(x) = x. This means that when you plug in the inverse function into the original function (or vice versa), you should get back the input value. If this holds true for all values in the domain, then the functions are indeed inverses of each other.

3. Can all functions have inverse functions?

No, not all functions have inverse functions. In order for a function to have an inverse, it must be one-to-one, which means that each input value has a unique output value. Functions that fail the horizontal line test, where a horizontal line intersects the graph of the function more than once, do not have inverse functions.

4. What is the relationship between the domain and range of a function and its inverse function?

The domain of a function becomes the range of its inverse function, and vice versa. This means that the inputs and outputs of the original function become the outputs and inputs, respectively, of the inverse function. It's important to note that the domain and range of the original and inverse functions may not be the same, as some values may be excluded due to restrictions.

5. How is the graph of a function related to the graph of its inverse function?

The graph of a function and its inverse are reflections of each other over the line y = x. This means that any point on the graph of the original function will have the coordinates (y, x) on the graph of its inverse function. Additionally, the x and y intercepts of the original function become the y and x intercepts, respectively, of the inverse function.

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