Proving Inverse Functions: Multiplicative Relationships

In summary, if ##f## and ##g## are multiplicative inverses of each other, then ##f^{-1} (x) = g^{-1} (\frac{1}{x})## can be formally proven by considering the function h which takes x to 1/x and using the fact that f = h \circ g and h = h^{-1}. This allows us to conclude that f^{-1} = g^{-1} \circ h, satisfying the given condition.
  • #1
PFuser1232
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Is there a way to formally prove that if ##f## and ##g## are multiplicative inverses of each other, then ##f^{-1} (x) = g^{-1} (\frac{1}{x})##?
 
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  • #2
I'd start by testing a number of special cases and see what approach the trickier special cases suggest.

Simple special cases almost never suggest approaches to proof, but the tricky special cases often do.
 
  • #3
MohammedRady97 said:
Is there a way to formally prove that if ##f## and ##g## are multiplicative inverses of each other, then ##f^{-1} (x) = g^{-1} (\frac{1}{x})##?

Let [itex]h[/itex] be the function which takes [itex]x[/itex] to [itex]1/x[/itex]. Now if [itex]f(x)g(x) = 1[/itex] for all [itex]x[/itex] then [itex]f = h \circ g[/itex]. Then [itex]f^{-1} = g^{-1} \circ h^{-1}[/itex]. But [itex]h = h^{-1}[/itex] so [itex]f^{-1} = g^{-1} \circ h[/itex] as required.
 
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  • #4
pasmith said:
Let [itex]h[/itex] be the function which takes [itex]x[/itex] to [itex]1/x[/itex]. Now if [itex]f(x)g(x) = 1[/itex] for all [itex]x[/itex] then [itex]f = h \circ g[/itex]. Then [itex]f^{-1} = g^{-1} \circ h^{-1}[/itex]. But [itex]h = h^{-1}[/itex] so [itex]f^{-1} = g^{-1} \circ h[/itex] as required.
Perfect. Thanks!
 

Related to Proving Inverse Functions: Multiplicative Relationships

1. What is an inverse function?

An inverse function is a mathematical operation that undoes another function. It is essentially the opposite of the original function and can be thought of as "reversing" the process.

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

To prove that two functions are inverses of each other, you must show that when the two functions are composed together, they result in the input value. In other words, if f and g are two functions, f(g(x)) = x and g(f(x)) = x.

3. Can all functions have an inverse?

No, not all functions have an inverse. For a function to have an inverse, it must be one-to-one, meaning that each input value maps to a unique output value. If there are multiple input values that result in the same output value, the function does not have an inverse.

4. How do you prove inverse functions using multiplicative relationships?

To prove inverse functions using multiplicative relationships, you must show that the product of the two functions is equal to the input value. In other words, if f and g are two functions, f(g(x)) = x and g(f(x)) = x. This is known as the multiplicative inverse property.

5. Are inverse functions always symmetrical?

Yes, inverse functions are always symmetrical. This means that the graph of an inverse function is a reflection of the original function over the line y = x. This is because the input and output values are switched in an inverse function, resulting in a symmetrical relationship.

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