Let u, u be functions of r. The first order derivative of uv can be derived by the following product rule: (uv)' = u'v+uv'. The general n-th order derivative of uv was obtained by the German mathematician Gottfried Wilhelm Leibniz: (uv) (") = (1) (4) (-4), k=0 n! = CR= k!(n-k)! By Leibniz's formula, compute f(100) (r) if where f(x) = (x + 2x+x+5) cosx.