Solution (source code)

= Solution

Using the ordered <orthonormal basis> chosen in (c), the column <matrix> is
$$
\boxed{B=\begin{pmatrix}
1/\sqrt2&1/\sqrt2&0\\
0&0&1\\
1/\sqrt2&-1/\sqrt2&0
\end{pmatrix}}.
$$
Other signs or another <orthonormal> choice within the repeated <eigenspace> are equally valid, provided the same choice is retained in the remaining parts.