Identity Matrix
#Math
$$\displaystyle I_{n}\in \mathbb{R}^{n}=
\begin{bmatrix}
1 & \ldots & 0 \\\vdots & \ddots & \vdots \\0 & \ldots & 1
\end{bmatrix}
$$
- $\displaystyle \delta_{ij}$ is the Kronecker Delta
#Math
$$\displaystyle I_{n}\in \mathbb{R}^{n}=
\begin{bmatrix}
1 & \ldots & 0 \\\vdots & \ddots & \vdots \\0 & \ldots & 1
\end{bmatrix}
$$