Differentiating Composition of Smooth Functions

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Homework Statement



Let f: M \rightarrow N, g:N \rightarrow K, and h = g \circ f : M \rightarrow K. Show that h_{*} = g_{*} \circ f_{*}.

Proof:

Let M,N and K be manifolds and f and g be C^\infinity functions.

Let p \in M. For any u \in F^{\infinity}(g(f((p))) and any derivation D at p.

[g \circ f)_* D](u) = D(u \circ g \circ f) = (f_{*}D)(u \circ g) = (g_{*}(f_{*}D))(u)

Homework Equations


The Attempt at a Solution

 
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Should be C^\infty and F^\infty(g(f((p)))
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...

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