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**The Pythagorean
rule and its application, according to a Greek manuscript of the 15th century
in Wien**

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**Maria D. Chalkou**

The Code 65 (Codex Vindobonensis phil. graecus 65) is made
of paper and dates from the 15^{th} century. In this Code (chapters
167–184), included are problems which are solved mainly by the use of the
Pythagorean rule or “the rule of skadra” (κανών της σκάδρας), as this was called
by the author of the Code. This article contains some chosen problems of chapters
167–184 and their mathematical comments. We tried an interpretative approach of
the methods of the Code’s author, as well as comparison of these with the
corresponding ones of today, which are taught in the secondary education.The
methodologies of finding answers even if in some cases they are not probably
used by the mathematicians of the secondary education, as we ascertain from the
examples which follow, adequate common factors with those used today in
corresponding problems.