4 ms·
Here's an even better one, which explains not only how Euler calculated logarithms with the bisection method, but also how he used some smart Taylor series tric
by credit_guy 3y ago
Here's an even better one, which explains not only how Euler calculated logarithms with the bisection method, but also how he used some smart Taylor series tricks too to get the (natural) logarithms of the integers from 1 to 10, with 25 decimals.
http://eulerarchive.maa.org/hedi/HEDI-2005-07.pdf http://eulerarchive.maa.org/hedi/HEDI-2005-07.pdf
How good was Euler at that? I checked his results with a multiple precision library (mpmath) and Euler got all the correct digits for 7 out of 10, he rounded off the last decimal in the wrong direction in 2 cases. Just for log(7) he got 21 correct decimals and the last 4 were wrong.
Here's the link to Euler's book [1], where these logarithms are on page 118. His values are
l1 = 0,00000 00000 00000 00000 00000
l2 = 0,69314 71805 59945 30941 72321
l3 = 1,09861 22886 68109 69139 52452
l4 = 1,38629 43611 19890 61883 44642
l5 = 1,60943 79124 34100 37460 07593
l6 = 1,79175 94692 28055 00081 24773
l7 = 1,94591 01490 55313 30510 54639
l8 = 2.07944 15416 79835 92825 16964
l9 = 2,19722 45773 36219 38279 04905
l10 = 2,30258 50929 94045 68401 79914
The correct values are
l1 = 0,00000 00000 00000 00000 00000
l2 = 0,69314 71805 59945 30941 72321
l3 = 1,09861 22886 68109 69139 52452
l4 = 1,38629 43611 19890 61883 44642
l5 = 1,60943 79124 34100 37460 07593
l6 = 1,79175 94692 28055 00081 24774
l7 = 1,94591 01490 55313 30510 53527
l8 = 2.07944 15416 79835 92825 16964
l9 = 2,19722 45773 36219 38279 04905
l10 = 2,30258 50929 94045 68401 79915
[1]https://scholarlycommons.pacific.edu/cgi/viewcontent.cgi?article=1100&context=euler-works https://scholarlycommons.pacific.edu/cgi/viewcontent.cgi?art...
- thaumasiotes 3y ago> and Euler got all the correct digits for 7 out of 10 This isn't the right denominator; you don't get any credit for calculating digits of ln(1).
- fsckboy 3y agoto be fair, you'd get marked off for getting ln(1) wrong, so I think we have to give credit for getting it right. (grading on a scale solves that problem, though i guess the gaussian hadn't been invented yet). the numerator is also "wrong"; of his 3 errors, 2 of them are wrong only "off by one" in the last digit, same direction both times, so without understanding the rounding rules in effect it's hard to know whether what happened is an actual error. ln(7) is a mess though but still at the least significant end.
- 3abiton 3y agoThat was a fun read
- credit_guy 3y agoHappy to hear. Here's another fun one, although much longer. https://www.math.ksu.edu/~cjbalm/570s14/briggs.pdf https://www.math.ksu.edu/~cjbalm/570s14/briggs.pdf It describes how Briggs created his table of logarithms with 14 decimal places, published in 1624, only 10 years after Napier published the first logarithms in 1614. Those times mush have felt like an incredible leap forward, probably similar to LLMs now. Kepler published his 3rd law of planetary motion in 1619. It would not have been possible to get that without logarithms, and it's quite likely that he knew of logarithms independently of Napier (who came up with them after some discussions with Kepler's boss, Tycho Brahe).
- jepler 3y agoInteresting that the log 7 case is called out as tricky in that linked PDF..