< M A T L A B (R) > (c) Copyright 1984-94 The MathWorks, Inc. All Rights Reserved Version 4.2c Nov 23 1994 matCommands to get started: intro, demo, help help Commands for more information: help, whatsnew, info, subscribe >> a=[1 -1 2; -1 2 -1; 0 2 1] a = 1 -1 2 -1 2 -1 0 2 1 >> b=inv(a) b = -4 -5 3 -1 -1 1 2 2 -1 >> a*b ans = 1 0 0 0 1 0 0 0 1 >> b*a ans = 1 0 0 0 1 0 0 0 1 >> a*b-eye(3) ans = 0 0 0 0 0 0 0 0 0 >> c=a' c = 1 -1 0 -1 2 2 2 -1 1 >> d=inv(c) d = -4.0000 -1.0000 2.0000 -5.0000 -1.0000 2.0000 3.0000 1.0000 -1.0000 >> c*d ans = 1.0000 0.0000 0.0000 0.0000 1.0000 -0.0000 0 0.0000 1.0000 >> d*c ans = 1.0000 0 0 0 1.0000 -0.0000 0 0 1.0000 >> c*d-eye(3) ans = 1.0e-14 * 0 0.0222 0.0444 0.0888 -0.0222 -0.1332 0 0.0222 0.0444 >> d*c-eye(3) ans = 1.0e-15 * 0 0 0 0 0 -0.8882 0 0 0 >> A=[1 2 -1 1; 0 -1 4 3; 4 2.6 0 3; 3 -0.3 8 1.5] A = 1.0000 2.0000 -1.0000 1.0000 0 -1.0000 4.0000 3.0000 4.0000 2.6000 0 3.0000 3.0000 -0.3000 8.0000 1.5000 >> B=inv(A) B = -0.5854 -0.1951 0.3780 0.0244 0.9408 -0.0436 -0.3397 0.1394 0.2613 0.0157 -0.1777 0.1498 -0.0348 0.2979 0.1237 -0.1533 >> A*B ans = 1.0000 0 0.0000 -0.0000 -0.0000 1.0000 0.0000 -0.0000 0.0000 0.0000 1.0000 0 0.0000 -0.0000 0.0000 1.0000 >> B*A ans = 1.0000 0.0000 0.0000 0.0000 0 1.0000 -0.0000 0.0000 0 0.0000 1.0000 0.0000 0 -0.0000 0 1.0000 >> A*B-eye(4) ans = 1.0e-15 * 0.2220 0 0.0416 -0.0555 -0.1110 0 0.1110 -0.1110 0.4441 0.1110 0 0 0.2220 -0.0555 0.2498 -0.1110 >> B*A-eye(4) ans = 1.0e-15 * 0 0.1076 0.2220 0.2429 0 0.2220 -0.4441 0.0555 0 0.0763 -0.2220 0.0555 0 -0.0347 0 -0.1110 >> a=[1 1; -2 -2] a = 1 1 -2 -2 >> b=inv(a) Warning: Matrix is singular to working precision. b = Inf Inf Inf Inf