Homework Help: Recursive Derivatives problem

1. Sep 26, 2004

Monsu

hi, could smne pls give me an idea of how to deal with this problem?

Suppose that f(0) = 0 and that f'(0) =1 , calculate f(f(f(x))) at point x=0
thanks a lot, any hint at all would b helpful, as i completely clueless.

2. Sep 26, 2004

vsage

if f(0) = 0 then f(f(0)) = f(0) = 0.. it's recursive. I am not sure why you would need f'(x) to solve nothing to do with derivatives. Are you sure you typed the question correctly?

3. Sep 26, 2004

Monsu

here it is again:
f(0) = 0 and f'(0) = 1 calculate the derivative of f(f(f(x))) at point x=0

that's the exact question.
thanks for the help on the second question

Last edited: Sep 26, 2004
4. Sep 26, 2004

vsage

Oh I see calculate the DERIVATIVE of f(f(f(0)))

First lets set g(x) = f(f(x))
g'(x) is therefore f'(f(x))*f'(x)

Derivative f(g(x)) after substitution is f'(g(x))*g'(x)

= f'(f(f(0)))*f'(f(0))*f'(0)

What a mouthful. If I were to venture a wild crazy guess I'd say that simplifies to 1.

5. Sep 26, 2004

Monsu

oh great! i just worked it out, it did come to 1. thanks a lot.
can u give a further hint on the other question, i'm still a bit confused there.
thanks again, marvellous!

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook