Describe all orthogonal matrices in $G$

72 Views Asked by At

If $G = \{ A \in GL(3,\mathbb R): Ax = x \}$, where $x = \begin{bmatrix} 1 \\ 0\\ 0 \\ \end{bmatrix}$, describe all orthogonal matrices in $G$.

1

There are 1 best solutions below

2
On BEST ANSWER

An orthogonal matrix represents an isometry of Euclidean space - it preserves the magnitude of any vector and the dot product of any two vectors. $G$ consists of the orthogonal $3 \times 3$ matrices which also leave the $x$ axis unchanged.

Your example is a family of orthogonal matrices, but they do not leave the $x$ axis unchanged. Instead, they map the $z$ acis to the $y$ axis.