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**Document integrity**: “Practical Application of Cryptographic Checksums”, with an introduction to applied cryptography.

**Scientific typesetting**: “Free Typesetting Software for the Professional Document Preparation”

**Software equipment**: “Introduction to Free Software and Operating Systems”

**News Ticker:**: Introduction to RSS

**Introduction to the indirect proof**:
“Proof of the Irrationality of the Square Root of 2”

Mathematical proofs are used to prove the correctness of formulas and assumed facts. Several basic procedures and ways of verifying mathematical correctness are in use, all of which follow a fixed scheme.

For the proof of the irrationality of the square root of 2 different proofs exist. This article explains the indirect proof variant in detail and introduces one of the possible short spellings in mathematical notation. Exercises with solutions consolidate what has been learned. 12 pages::

A4 • A4 duplex • US-Letter • US-Letter duplex

**School mathematics**: Detailed solutions to the first 27 text problems of
“A first book in Algebra”, author Wallace C. Boyden,
added, a textbook for beginners in algebra:
Text problems with solutions, 10 pages (PDF, A4 format, in English)..

**Freiburg i.Br.:**
“Freiburg Excursion Destinations and Film Recommendations”

As of: August 21, 2022

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