Function Fi Help: Simplifying the (m,n)=d Demonstration

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SUMMARY

The discussion focuses on the mathematical demonstration of the relationship between the greatest common divisor (gcd) and the Euler's totient function, specifically the equation \(\Phi(mn) = \frac{d}{\Phi(d)}\Phi(m)\Phi(n)\) when \((m,n)=d\). The variables \(m\) and \(n\) are expressed in terms of their prime factorization, \(m = p^{\kappa_{1}}_{1}...p^{\kappa_{r}}_{r}\) and \(n = p^{\beta_{1}}_{1}...p^{\beta_{r}}_{r}\), leading to the gcd representation \((m,n) = p^{\delta_{1}}_{1}...p^{\delta_{r}}_{r}\) where \(\delta_{i} = \min\{\kappa_{i},\beta_{i}\}\). The function \(\Phi(w)\) is defined as \(w\prod^{i=1}_{r} (1-1/p_{i})\), which is crucial for deriving the desired result.

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  • Understanding of prime factorization
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catala
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Hi,

I need help in the following demonstration:

If (m,n)=d then \Phi(mn)=\frac{d}{\Phi(d)}\Phi(m)\Phi(n)

Thank you very much for your support! :D
 
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Ok, so first begin by letting m= p^{κ_{1}}_{1}...p^{κ_{r}}_{r} and n=p^{β_{1}}_{1}...p^{β_{r}}_{r}, where κ_{i},β_{i}≥ 0 \foralli. Then (m,n)= p^{δ_{1}}_{1}...p^{δ_{r}}_{r}, where δ_{i} = min{κ_{i},β_{i}}. Then use the fact that \Phi(w) = w∏^{i=1}_{r} (1-1/p_{i}), given that w = p^{κ_{1}}_{1}...p^{κ_{r}}_{r} to rewrite \Phi(mn). At this point, it isn't too difficult to come up with the desired result. If you rewrite the right side of what you are trying to prove, it helps to at least see where you should go next.

Also, as a side note, \Phi is spelled 'phi' :-p
 

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