Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Crelle's tables
    From: Bill Ritchie
    Date: 2020 Sep 27, 22:55 +0100
    Fabulous, Lars. This had me recalling schoolboy algebra expansions to realise that all the terms cancelled except for 2a.b/4 + 2a.b/4, which equals a.b.

    Snippets like this one are great, adding to the library of quality information on NavList from Frank and so many knowledgeable contributors. 

    Bill Ritchie.

    On Sun, Sep 27, 2020 at 10:01 PM Lars Bergman <NoReply_Bergman@fer3.com> wrote:

    Crelle's table is some 450 pages, and it gives the result directly for the multiplication of two integers less than 1000. With slightly more work, but only two and a half pages for a similar range, a table of "quarter squares" does the same job. Such a table (of total 14 pages covering integers up to 5100) is included in Chamber's Seven-Figure Mathematical Tables. It works on the fact that

    a·b = (a+b)2/4 - (a-b)2/4

    Find out a+b and a-b, look up their quarter squares in the table and take their difference.


    View and reply to this message

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site