Does dividing a function by a smooth function result in a smooth function?

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The discussion centers on whether the smoothness of a function raised to powers implies the smoothness of the original function. It questions if the conditions f·f and f·f·f being smooth (C^∞) necessitate that f itself is also smooth. Participants consider the implications of generalizing this to f^n and f^(n-1) being smooth and whether this leads to the conclusion that f is smooth. The conversation highlights the need to understand the relationship between division and smoothness in functions. Ultimately, the inquiry seeks to clarify the conditions under which smoothness is preserved through operations on functions.
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If f \cdot f and f \cdot f \cdot f is smooth, does it follow that f is smooth?

So does f \cdot f \in C^{\infty} \ \text{and} \ f \cdot f \cdot f \in C^{\infty} \Rightarrow f \in C^{\infty}?

Maybe we could generalize a bit more: Given that f^{n} , f^{n-1} \in C^{\infty} does it follow that f \in C^{\infty} (where f^n is the function raised to some power n)?
 
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