%%visits: 3 orthogonal_grou := O(N) = {A ∈ GL(n, ℝ)|AT = A−1}
theorem. A real linear transformation A of ℝn is such that ∣Ax̂∣ = ∣x̂ ∣ ∀x ∈ ℝn
if and only if A ∈ O(n)
If x̂ ∈ ℂn is a [[eigenvector]] of A ∈ O(N) with [[eigenvalue]] λ then |λ| = 1
If $\underline{x} \in \mathbb{C}$ is an [[eigenvector]] of A ∈ O(n) with [[eigenvalue]] |λ| = 1
1 is in the spectrum of A ∈ O(n). ## exam clinic ## examples and non-examples ## resources [[special_orthogonal_group]] tags math__groups_and_symmetries: