Exercises. (1) Let a, a, be a sequence of real numbers. Prove that 2 n Ση Σα i=1 (2) Compute the cosine of the angle between the following pairs of vectors. (E) (A) and v= -(-4). (b) In R³, the vectors u and v = (a) In R², the vectors u = (c) In R4, the vectors u = and v = (d) In R5, the vectors u = 1 1 and v =

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