Corollary 5. If the composition (fn o • • • o f)(x) of differentiable functions
V = / i W , • • •, Vn = fn(yn-i) exists, then
(fn o . • . O ftfix) = f'n(Vn-l)f'n-l(Vn-2) ' ' ' / { ( * ) •
Proof The statement is obvious if n = 1.
If it holds for some n G N, then by Theorem 2 it also holds for n + 1, so
that by the principle of induction, it holds for any n G N. •