Definition:Orthogonal Matrix

Definition
Let $\mathbf Q$ be a square matrix.

Then $\mathbf Q$ is orthogonal :
 * $\mathbf Q^{-1} = \mathbf Q^\intercal$

where:
 * $\mathbf Q^{-1}$ is the inverse of $\mathbf Q$
 * $\mathbf Q^\intercal$ is the transpose of $\mathbf Q$