Triangular matrix

Lower Triangular matrix

$\begin{bmatrix}
e_{11} & 0 & 0 & \cdots & 0\\
e_{21} & e_{22} & 0 & \cdots & 0\\
e_{31} & e_{32} & e_{33} & \cdots & 0\\
\vdots & \vdots & \vdots & \ddots & \vdots\\
e_{n1} & e_{n2} & e_{n3} & \cdots & e_{nn}
\end{bmatrix}$

Upper Triangular matrix

$\begin{bmatrix}
e_{11} & e_{12} & e_{13} & \cdots & e_{1n}\\
0 & e_{22} & e_{23} & \cdots & e_{2n}\\
0 & 0 & e_{33} & \cdots & e_{3n}\\
\vdots & \vdots & \vdots & \ddots & \vdots\\
0 & 0 & 0 & \cdots & e_{nn}
\end{bmatrix}$

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