matlab basics : matrix norms, condition number

A =

     1     0    -2
     2     2     2
     2     2     4

>> norm(A)

ans =

    6.0225

%infinity norm

>> norm(A,'inf')

ans =

     8


%condition numbers
>> cond(A)  

ans =

   19.5212

>> cond(A,'inf')

ans =

    36

>> norm(A)*norm(inv(A))

ans =

   19.5212

>> norm(A,'inf')*norm(inv(A),'inf')

ans =

    36