A square matrix such that , where is the identity matrix. An involutory matrix is its own matrix inverse.
Involutory Matrix
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References
Ayres, F. Jr. Schaum's Outline of Theory and Problems of Matrices. New York: Schaum, p. 11, 1962.Referenced on Wolfram|Alpha
Involutory MatrixCite this as:
Weisstein, Eric W. "Involutory Matrix." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/InvolutoryMatrix.html