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    Re: Degree Calculator
    From: David C
    Date: 2018 Nov 27, 18:13 -0800

    This thread has started me thinking about the various calculator entry methods. Was any research done on this subjact just as xerox researched the gui and
    mouse (and other companies borrowed it)?

    My starting point is the expression

    2x3  +  6x5

    A quick bit of mental arithmetic gives the answer 36.


    On the fx-82-AU 8 keystrokes are required:

    2x3  +  6x5 =


    Next I tried Realcalc in non-rpn mode. 12 keystrokes gave me the answer:

    2 x 3 = STO 6 x 5 = + RCL =

    I suspect that in the 1970s calculators did not have enought commputing  power to provide for natural entry so other conventions were necessary.


    Finally, several decades after last using RPN, I decided to give it a go. 9  keystrokes gave the answer:

    2 enter 3  X

    6 enter 5  X



    Because I had successfully rediscovered RPN I decided to compute Hc with RPN.

    The equation is

    arc sin (sinA SinB + CosA*CosB*CosC)

    After some playing around I came up with

    A DMS  Sto 0
    B DMS  STO 1
    C DMS  cos
    x<->y  cos  X  x<->y
    cos X                     /* part 2 of expression complete */

    rcl 0  sin
    rcl 1 sin
    X                         /* part 1 of expression complete */

    arc sin

    The next step was to try a real example:

    A = 20°  (dec)
    B = 40° (lat)  same names
    C = 30°  (t)

    The RPN answer was  57° 29'

    Getting my copy of AP3270 from the bookshelf the solution was 57° 29'           Amazing!!!!!!!!!!!

    As a triple check I calculated Hc  on my fx-82AU. The answer was  57° 30'. I can remember rounding up.

    IMHO the advantage of the fx-AU over Realcalc is that provided  power is kept on the  expression is stored and it is only becessary to enter the new values for each sight.

    Also the fx-AU has proper buttons rather than a touch screen - strange things kept happening with Realcalc until I realised that I had to keep all parts of my hand away from the screen. For speedy evaluation of an expression I much prefer hard buttons.   Everything today seems to use touch screens -  presumably to reduce cost. My printer has hard buttons but if I purchased it today it would have a touch screen.  When I see photos of glass cockpits in aircraft I pray that vital navigation equipment has real buttons for data entry!


    In the google play store I found an app called gforth. I installed it but it crashed when I tried to use it so that is the end of that.

    I may search for a Forth interpreter that I can run on my PC.

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