# Analytic proof

1. Jun 28, 2008

### mathwizarddud

Suppose the real valued $$g$$ is defined on $$\mathbb{R}$$ and $$g'(x) < 0$$ for every real $$x$$. Prove there's no differentiable $$f: R \rightarrow R$$ such that $$f \circ f = g$$.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Jun 28, 2008