The identity matrix is the matrix for which a_ij = 1 when i = j, and 0 everywhere else. For example, in three dimensions, I = [[1 0 0 ; 0 1 0 ; 0 0 1]]. Here is a column vector: [[0 1 0]]'. x \mapsto y_1...y_n 1/3 1 + 1 = 2 1 \leq 3 - 1 \leq 5 \begin{graph} rankdir=LR v_1 v_1 -> v_2 v_2 -> v_3 v_3 -> v_1 \end{graph} %% note: dollar sign placement cannot be auto-detected on the v2->v3 edge %% because of the commas