Cosine-based Similarity
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### Cosine-based Similarity

In this case, two items are thought of as two vectors in the m dimensional user-space. The similarity between them is measured by computing the cosine of the angle between these two vectors. Formally, in the ratings matrix in Figure 2, similarity between items i and j, denoted by sim(i,j) is given by

where '' denotes the dot-product of the two vectors.