IsInvolution
Tests if a matrix is an involution.
Syntax

IsInvolution(A[, ε])

A
is a matrix 
ε
is a positive number

Description
IsInvolution(A, ε)
returns true
iff A
is an involution, that is, iff A = A^−1
, using ε
as the epsilon for floatingpoint comparisons. Equivalently, A
is invertible and A^2 = I
(the identity matrix).
Examples
A ≔ ReflectionMatrix(❨3, 1, −2❩)
⎛−0.285714285714 −0.428571428571 0.857142857143⎞ ⎜−0.428571428571 0.857142857143 0.285714285714⎟ ⎝ 0.857142857143 0.285714285714 0.428571428571⎠
IsInvolution(A)
true