let n be Nat; :: thesis: for M1, M2 being Matrix of n, REAL holds
( len M1 = len M2 & width M1 = width M2 )
let M1, M2 be Matrix of n, REAL ; :: thesis: ( len M1 = len M2 & width M1 = width M2 )
( width M1 = n & width M2 = n & len M1 = n & len M2 = n ) by MATRIX_1:25;
hence ( len M1 = len M2 & width M1 = width M2 ) ; :: thesis: verum