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Vector Cosine

For real vectors x and y having the same length, we may compute the vector cosine by
cosxy = y' * x / ( norm(x) * norm(y) );
For complex vectors, a good measure of orthogonality is the modulus of the vector cosine:
collinearity = abs(y' * x) / ( norm(x) * norm(y) );
Thus, when collinearity is near 0, the vectors x and y are substantially orthogonal. When collinearity is close to 1, they are nearly collinear.

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Inner Product