1/04/2023

What happens if we graph both f and f^{-1} on the same set of axes, using the x-axis for the input to both f and f^{-1} ?

 What happens if we graph both f and f^{-1} on the same set of axes, using the x-axis for the input to both f and f^{-1} ? 

Suppose f:R \rightarrow R is a function from the set of real numbers to the same set with f(x)=x+1. We write f^{2} to represent f \circ f and f^{n+1}=f^n \circ f. Is it true that f^2 \circ f = f \circ f^2? Why? Is the set {g:R \rightarrow R l g \circ f=f \circ g} infinite? Why? 

Inherently, the range of a function f (x) is the domain of the inverse function f^{-1}. The domain of f  is the range of  (f^{-1} \circ f)(x)=f^{-1}(f(x))=f^{-1}(y)=x  So, what happens if we graph both f and f^{-1} on the same set of axes, using the x-axis for the input to both f and f^{-1} ? Let's try some examples.

If we type y=x^3  \lbrace{-2 < x < 2}\rbrace y=x^{1/3}  \lbrace{-2 < x < 2}\rbrace , and  y = x   \lbrace{-2 < x < 2}\rbrace  on the graph, all of the three functions will be limited in the same input   \lbrace{-2 < x < 2}\rbrace    and their output will also affected by such a input boundary. The domain of f  become the domain of  (f^{-1} \circ f)(x)  , not its range. 




Let's try another example: C° to F°: Celsius to Fahrenheit Conversion Formula

 F = C×( \frac{9}{5} )+32

 F^{-1} = (\frac{9}{5})(C-32)





Again, as we can see that these these three lines are more like projections of each other from different angles rather than reflection.

The difficulty of setting the same set of axes for f and f^{-1} is that f^{-1} will become not fully or true inverse function of f  since the output of f^{-1} is limited. Instead of setting the input {-100 < x < 100}, the input of  f^{-1}  should be the range of f 


Suppose f:R \rightarrow R is a function from the set of real numbers to the same set with f(x)=x+1. We write f^{2} to represent f \circ f and f^{n+1}=f^n \circ f

When f^{n+1}=f^n \circ f.  and  n \geq1

 f^2=f \circ f

If f^{2} represents f \circ f  =f(f(x))  ,  f^2 \circ f =f^2(f(x))  
 f^2=f(x+1)=(x+1)+1=x+2

It is similar to an arithmetic progression which the next one is the previous number +1

Recall that  f^2=f \circ f=f(f(x))   
 f^2 \circ f=f(f(f(x)))
 f \circ f^2=f(f^2(x))=f(f \circ f)=f(f(f(x)))
Therefore,  f^2 \circ f = \( f \circ f^2 = \( f(f(f(x)))

 g \circ f =g(f(x)) = f \circ g=f(g(x))
In this case,  f(x)=x+1    g(f(x))=g(x+1)=g(x)+1=f(g(x))
Now, we know that the set has to satisfy the equation  g(x+1)=g(x)+1  
If the domain of  g(x)  is all real numbers, then g(1)=g(0)+1, g(2)=g(1)+1, g(3)=g(2)+1,....... it will be infinite.

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.

ReadingMall

BOX