What is the name of the property of a function that yields the original result when done twice in a row:
$$f(f(x)) = x?$$
I'm pretty sure there is a word for these functions, but I haven't been able to find it.
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7The are often called involutions (which generally means something that squares to the identity). – Tobias Kildetoft May 09 '16 at 08:01
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A function that has this property is known as an involution.
Such functions are interesting to study, as they are their own inverse $$f^{-1}(x) = f(x)$$
Some examples:$$f(x) = x\\f(x) = \frac{a}{x}\\f(x) = a - x\\f(x) = a + \frac{b}{x-a}$$
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