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    Re: Hc formula difference why?
    From: John D. Howard
    Date: 2017 Nov 21, 17:35 -0800

    Herman,

    Think logarithmns and negative numbers.

    Not so long ago if you wanted to multiply or divide you used log tables ( or slide rules - same thing ) but there are no logs for negative numbers.

    The work-around was to work in positive numbers and then have rules like " If same name, subtract; if contary name, add".  By using mederian angle, T, and not GHA you could limit angles to 0 to 90 d.  Another work-around was the weird trig functons like haversine where there are no negative numbers.  We, today, think nothing of South dec being negative or West long being negative but still, I for one, must rember to ADD when subtracting a negitive number.

    The " ~ " was used with some rule - usually when to add or subtract.  Like many have pointed out, the formulas are the same.

    John H.

       
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