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    Re: The Bygrave Slide rule
    From: Gary LaPook
    Date: 2009 May 29, 18:24 -0700

    I haven't had the chance to investigate your comments but I am not
    married to my analysis of Bygrave's method. We both agree that one of
    the scales is an inverse scale since they both run in the same
    direction and that Bygrave didn't tell us that. When I tried to figure
    it out I came to the conclusion that the tangent scale had been
    inverted but I can see your point that it could be the cosine scale. I
    think that I read that the Dennert & Pape MHR-1 has a co-tangent scale
    and the Bygrave looks just like it so it made sense that the Bygrave
    also had the inverse tan scale. I am planning to spend some time this
    weekend really delving into this further.
    
    I would appreciate a copy of Aquino's method, can you send it to me
    off list?
    
    I am really enjoying this deep analysis of the Bygrave slide rule and
    it may turn out that Captain Bygrave was more brilliant than we
    originally thought.
    
    gl
    
    On May 29, 2:39�pm,  wrote:
    > It's just been drawn to my attention that in the book "Spherical 
    Trigonometry" by J.H. Clough-Smith, on page 105, "Aquino's log tangent + log 
    secant method" is described. It seems fairly clear that the Bygrave Slide 
    Rule is based on this method, which talks about 'only needing tables of log 
    secants and log tangents'.
    >
    > I rest my case. �Bygrave must have consciously changed the name 'secant' to 
    'cosine' in his written descriptions.
    >
    > I have a .gif of this description but as a non-member I can't post it here.
    >
    > Peter Martinez
    >
    > --------------------------------------------------------
    > [Sent from archive by: peter.martinez-AT-btinternet.com]
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