My dad showed me the method of successive trials to solve intractable problems. When I had my HP65 I found I could enter the variables in storage and do a repeatted solution without effort. I was working with negatice temperature coefficient thermistors and had tabulated resistances but no formula. I tried until I found that adding a large number to the temperature and take the Ln I could match the slope of the resistance temperature curve over the complete range. I could refine the precision by repeated trials. To date this has not been discovered, but an extremely compleex method is used and they are not going to change. I thought I could match other graphs I used in electrical engineering and by trial and error matched many of them. I was interested in retirement and matched income tax in my renge, and made varied assumptions of inflation, return on investments, raises and solved them year by year. I found all you needed was to make more money than you spent and you could pay your way. I did not depend on SS or retirement benefits, I thought them unworkable schemes. So I'm good at 82 and will leave an income for my niece to sustain her.
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HP 65 programmable
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