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| -rw-r--r-- | doc/exercises.tex | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/doc/exercises.tex b/doc/exercises.tex index ebf8e91..14123d2 100644 --- a/doc/exercises.tex +++ b/doc/exercises.tex @@ -262,10 +262,13 @@ which calculates the totient of $n$. Its formula is \( \displaystyle{ - \varphi(n) = n \prod_{p \in \textbf{P} : p | n} + \varphi(n) = |n| \prod_{p \in \textbf{P} : p | n} \left ( 1 - \frac{1}{p} \right ). }\) +Note that, $\varphi(-n) = \varphi(n)$, $\varphi(0) = 0$, +and $\varphi(1) = 1$. + \end{enumerate} @@ -671,7 +674,8 @@ So, if we set $a = n$ and $b = 1$, then we iterate of all integers $p$, $2 \le p \le n$. For which $p$ that is prime, we set $a \gets a \cdot (p - 1)$ and $b \gets b \cdot p$. After the iteration, $b | a$, -and $\varphi(n) = \frac{a}{b}$. +and $\varphi(n) = \frac{a}{b}$. However, if $n < 0$, +then, $\varphi(n) = \varphi|n|$. |