Ma trận nào sau đây không phải là ma trận trực giao:

\[\left( {\begin{array}{*{20}{c}}{\cos \varphi }&{ - \sin \varphi }&0\\{\sin \varphi }&{\cos \varphi }&0\\0&0&{ - 1}\end{array}} \right)\]

\[\left( {\begin{array}{*{20}{c}}\begin{array}{l}\frac{3}{5}\\\frac{4}{5}\end{array}&\begin{array}{l}\frac{4}{5}\\\frac{{ - 3}}{5}\end{array}\end{array}} \right)\]

\[\left( {\begin{array}{*{20}{c}}{\frac{2}{3}}&{\frac{1}{3}}&{\frac{2}{3}}\\{\frac{{ - 2}}{3}}&{\frac{2}{3}}&{\frac{1}{3}}\\{\frac{{ - 1}}{3}}&{\frac{{ - 2}}{3}}&{\frac{2}{3}}\end{array}} \right)\]

\[\left( {\begin{array}{*{20}{c}}0&{\frac{{ - 1}}{{\sqrt 2 }}}&{\frac{1}{{\sqrt 2 }}}\\{\frac{1}{{\sqrt 2 }}}&0&{\frac{1}{{\sqrt 2 }}}\\{\frac{1}{{\sqrt 2 }}}&{\frac{1}{{\sqrt 2 }}}&0\end{array}} \right)\]