1. Vedran Miletić
  2. beamer
Issue #96 resolved

Documentation: Bug in Euclid's proof

Sebastian Korten
created an issue

There is a problem with euclids proof in the tutorial at the beginning of the beamerguide --- it is wrong.\

By the stated proof (13! + 1) should be prime, which it is not (it's 83 * 75024347).\ [Furthermore: (17!+1) = 538105034941 * 661 and (19! +1) = 1713311273363831 * 71)]\

It it true that (19!+1) is not divisible by any integer <= 19, but that is definitely not enough to prove that it is prime.\

You will find euclids proof explained here:\ http://aleph0.clarku.edu/~djoyce/java/elements/bookIX/propIX20.html\

The reason why I report this as a bug is that I read the beamer documentation some years ago and up until two days ago I thought the proof was valid ;o)

I hope you understand that this 'bugs' me ;o)

Btw, I love beamer. Thank you so much for your effort!

Comments (8)

  1. Sebastian Korten reporter

    This would be a possible fix:

    \begin{proof}
    \begin{enumerate}
    \item<1-> Suppose $P$ is a set containing all known prime numbers
    \item<2-> $q = (\prod\limits_{x\in P}{x}) + 1$
    \item<3-> $q$ is not divisible by any number in $P$
    \item<4-> \alert{Either} $q$ is prime and $q \not\in P$
    \item<5-> \alert{or} $q$ is not prime, but has at least two prime factors $a, b \not\in P$
    \item<6-> $\Rightarrow$ there are more prime numbers than those in $P$\qedhere
    \end{enumerate}
    \end{proof}

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