% Computes an inverse matrix using row operations.
disp('Computation of the inverse matrix')
disp('Press a key to continue.')
A = [1 2 1; 1 3 2; 1 0 1]    
pause
AA = [A eye(3)]                
pause
E21= eye(3);
E21(2,1) = -1                   
pause
E31  = eye(3);
E31(3,1) = -1                   
pause
E32 = eye(3);
E32(3,2) = 2                    
pause
disp('UU = E32*E31*E21*AA')
UU = E32*E31*E21*AA   
pause
display(' Inverse of A = UU(1:3,1:3)\UU(1:3,4:6)')
B = UU(1:3,1:3)\UU(1:3,4:6)    
pause
disp('AB = A*B')
AB = A*B              
pause
disp('BA = B*A')
BA =B*A              
pause
disp('Inverse of A = inv(A)')
inv(A)          
pause
disp('Inverse of a block diagonal matrix')
pause
D1 = [2 -1;-1 2]                               
pause
D2 = [2 -1 0;-1 2 -1; 0 -1 2]             
pause
A = [D1 zeros(2,3);zeros(3,2) D2]   
pause
disp('B1 = inv(A)')
B1 = inv(A)                                        
pause
disp('B2 = [inv(D1) zeros(2,3);zeros(3,2) inv(D2)]')
B2 = [inv(D1) zeros(2,3);zeros(3,2) inv(D2)]