I’m studying for my Computer Science class and need an explanation.
I will attached the Text book
This discussion is based on problem 27 in chapter 2: Show that the distance measure defined as the angle between two data vectors, x and y, satisfies the metric axioms given on page 70. Specifically, angle between two data vectors is arccos( cos(x,y) ), so d(x, y) = arccos( cos(x,y) )
Show for distance measure arccos( cos(x,y) )
A) Positivity
1) d(x,x) >= 0 for all x and y,
2) d(x,y) == 0 onlY if x == y.
B) Symmetry
d(x,y) == d(y,x) for all x and y.
C) Triangle Inequality
d(x,z) < d(x,y) + d(y,z) for all points x, y, and z.
D) Explain in simple English the intuition for why would arccos( cos(x,y) ) satisfy the same properties (A,B,C above) as the Euclidean distance.



