MHB Inverse Functions: Reflection of f(x) & g(x) Logic

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The discussion centers on the relationship between a function \(f(x)\) and its inverse \(g(x)\). It highlights that if a point \((x, f(x))\) exists on the graph of \(f(x)\), then the corresponding point \((f(x), x)\) will be on the graph of \(g(x)\). The conversation emphasizes the significance of the mid-point locus, which is \(\left(\frac{x+f(x)}{2}, \frac{x+f(x)}{2}\right)\). This leads to the conclusion that the line of symmetry for the functions is \(y = x\). Understanding this symmetry is crucial for grasping the concept of inverse functions.
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Can anyone explain the logic behind the answer?

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Suppose we have the point:

$$(x,f(x))$$

on the plot of \(f(x)\). Then, on the plot of \(g(x)\), we must have the corresponding point:

$$(f(x),x)$$

Now, consider that for all possible points, the locus of the mid-points is:

$$\left(\frac{x+f(x)}{2},\frac{x+f(x)}{2}\right)$$

Thereby implying that the line of symmetry must be:

$$y=x$$
 
Here is a little puzzle from the book 100 Geometric Games by Pierre Berloquin. The side of a small square is one meter long and the side of a larger square one and a half meters long. One vertex of the large square is at the center of the small square. The side of the large square cuts two sides of the small square into one- third parts and two-thirds parts. What is the area where the squares overlap?

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