let K be Field; for A being Matrix of 0 ,K holds
( A = {} & A = 1. K,0 & A = 0. K,0 )
let A be Matrix of 0 ,K; ( A = {} & A = 1. K,0 & A = 0. K,0 )
A1:
len A = 0
by MATRIX_1:25;
hence
A = {}
; ( A = 1. K,0 & A = 0. K,0 )
hence
A = 1. K,0
by Th14; A = 0. K,0
thus
A = 0. K,0
by A1; verum