how do I prove The second formula from Euler's totient function ?
$\sum_{\substack{1\le k\le n\\(k,n)=1}} k=\frac 12 n \varphi(n)$ for $n>1$.
how do I prove The second formula from Euler's totient function ?
$\sum_{\substack{1\le k\le n\\(k,n)=1}} k=\frac 12 n \varphi(n)$ for $n>1$.
We know that there are exactly $\phi(m)$ integers less than $m$ and relatively prime to $m$. Also if a
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