let n be Nat; :: thesis: for M1, M2 being Matrix of n,REAL st - M1 is_less_or_equal_with M2 holds
M1 + M2 is Nonnegative
let M1, M2 be Matrix of n,REAL; :: thesis: ( - M1 is_less_or_equal_with M2 implies M1 + M2 is Nonnegative )
A1: Indices M1 = [:(Seg n),(Seg n):] by MATRIX_0:24;
A2: Indices (- M1) = [:(Seg n),(Seg n):] by MATRIX_0:24;
A3: Indices (M1 + M2) = [:(Seg n),(Seg n):] by MATRIX_0:24;
assume A4: - M1 is_less_or_equal_with M2 ; :: thesis: M1 + M2 is Nonnegative
for i, j being Nat st [i,j] in Indices (M1 + M2) holds
(M1 + M2) * (i,j) >= 0

proof

let i, j be Nat; :: thesis: ( [i,j] in Indices (M1 + M2) implies (M1 + M2) * (i,j) >= 0 )
assume A5: [i,j] in Indices (M1 + M2) ; :: thesis: (M1 + M2) * (i,j) >= 0
then (- M1) * (i,j) <= M2 * (i,j) by A4, A2, A3;
then - (M1 * (i,j)) <= M2 * (i,j) by A1, A3, A5, Th2;
then (M1 * (i,j)) + (M2 * (i,j)) >= 0 by XREAL_1:60;
hence (M1 + M2) * (i,j) >= 0 by A1, A3, A5, MATRIXR1:25; :: thesis: verum

end;

hence M1 + M2 is Nonnegative ; :: thesis: verum