Identity matrix, scalar matrix (quantity matrix) and diagonal matrix are all 0 except diagonal.
Diagonal of that unit array are all 1,
The diagonal lines of scalar matrices (number matrices) are all represented by the same number λ (so scalar matrices are all pure numbers λ, but the tutor of the postgraduate entrance examination teacher also uses K, which means the same thing. It may be called number matrix because it is special and can satisfy the commutative law like numbers, so it is called number matrix, because other matrix multiplication generally cannot use commutative law).
There are several λ 1, λ2, ... about the diagonal of diagonal matrix. Each number is not necessarily the same, but it is a scalar matrix (quantity matrix).
Representation symbol:
The unit array is represented by e.
Scalar matrix (quantity matrix) is represented by λE (some teachers in postgraduate entrance examination use kE, which means the same thing).
The diagonal matrix is denoted by λ.
The relationship between them is:
The mathematical symbol is: e ∈ λ e ∈ λ, (If the symbol really contains it, you don't have to type it, just type it here. )
Chinese symbols indicate that identity matrix belongs to scalar matrix (quantity matrix) and diagonal matrix. Or diagonal matrix really contains scalar matrix and identity matrix.
Handmade, it helps. Give me a compliment. Thank you, hahaha.