# Question

Let f: R→R 2. Prove that f is differentiable at a € R if and only if f 1 and f 2 are, and in this case

f 1(a) = ((f 1)1 (a) (f 2)1 (a)).

f 1(a) = ((f 1)1 (a) (f 2)1 (a)).

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