let M1, M2 be Matrix of REAL; :: thesis: ( len M1 = len M & width M1 = width M & ( for i, j being Nat st [i,j] in Indices M holds
M1 * (i,j) = |.(M * (i,j)).| ) & len M2 = len M & width M2 = width M & ( for i, j being Nat st [i,j] in Indices M holds
M2 * (i,j) = |.(M * (i,j)).| ) implies M1 = M2 )

assume that
A6: len M1 = len M and
A7: width M1 = width M and
A8: for i, j being Nat st [i,j] in Indices M holds
M1 * (i,j) = |.(M * (i,j)).| and
A9: ( len M2 = len M & width M2 = width M ) and
A10: for i, j being Nat st [i,j] in Indices M holds
M2 * (i,j) = |.(M * (i,j)).| ; :: thesis: M1 = M2
now :: thesis: for i, j being Nat st [i,j] in Indices M1 holds
M1 * (i,j) = M2 * (i,j)
let i, j be Nat; :: thesis: ( [i,j] in Indices M1 implies M1 * (i,j) = M2 * (i,j) )
assume A11: [i,j] in Indices M1 ; :: thesis: M1 * (i,j) = M2 * (i,j)
A12: dom M1 = dom M by ;
hence M1 * (i,j) = |.(M * (i,j)).| by A7, A8, A11
.= M2 * (i,j) by A7, A10, A11, A12 ;
:: thesis: verum
end;
hence M1 = M2 by ; :: thesis: verum