How would I go about proving $\delta_{ij}$ is a rank 2 tensor? Help appreciated
EDIT: Tensor being defined by the following:
$$x'_i = L_{ij} x_j, x_i = L_{ji} x'_j \tag{7.7}$$
A Cartestian Tensor $T_{ij...l}$ of rank $r$ has $r$ indices and transforms under the special orthogonal transformation $(7.7)$ as
$T^{'}_{ij...l}$($x^{'}$) = $L_{ip}$$L_{jq}$...$L_{ls}$$T_{pq...s}$($L^{-1}$$x^{'}$)
The definition of $\delta_{ij}$ is independent of the basis chosen. If $R$ is a rotation matrix, then since $R^\intercal R=I$, we get $$R_{ip}R_{jq}\delta_{pq}=R_{ip}R_{jp}=\delta_{ij}=\delta_{ij}',$$ which is precisely the transformation rule for a rank $2$ tensor.