Involution (mathematics)

For other uses, see Involution (disambiguation) § Mathematics.
An involution is a function f : X → X that, when applied twice, brings one back to the starting point.

In mathematics, an involution, involutory function, or self-inverse function[1] is a function f that is its own inverse,

f(f(x)) = x

for all x in the domain of f.[2] Equivalently, applying f twice produces the original value.

  1. ^ Robert Alexander Adams, Calculus: Single Variable, 2006, ISBN 0321307143, p. 165
  2. ^ Russell, Bertrand (1903), Principles of mathematics (2nd ed.), W. W. Norton & Company, Inc, p. 426, ISBN 9781440054167