title: matrix.dot(inv(matrix)) isn't equal to identity matrix
body: <p>I'm encountering an issue since hours, I don't understand why the V matrix below doesn't equal the Identity matrix:</p>
  
  <pre><code>A = np.random.randint(50, size=(100, 2))
  V = A.dot(A.T)
  D = V.dot(inv(V))
  D
  </code></pre>
  
  <p>The result I found is below either:</p>
  
  <pre><code>array([[  3.26611328,   7.87890625,  14.1953125 , ...,   2.        ,
       -5.        , -24.        ],
     [ -5.91061401, -26.05834961,   5.30126953, ..., -10.        ,
        8.        , -16.        ],
     [ -2.64431763,   3.55639648,   3.10107422, ...,  -0.5       ,
       -5.        ,  -4.        ],
     ...,
     [ -2.62512207,  -7.78222656,  10.26367188, ...,  -6.        ,
       18.        ,   0.        ],
     [ -3.0625    ,  14.        ,  -4.        , ...,  -0.0625    ,
        0.        ,   8.        ],
     [  2.        ,  -7.        ,  16.        , ...,  -7.5       ,
       -8.        ,  -4.        ]])
  </code></pre>
  
  <p>Thank you for your help</p>