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The math behind a neat calculator trick (divisbyzero.com)
74 points by signa11 on April 27, 2010 | hide | past | favorite | 17 comments


If you want to work it out yourself first here is the trick. Set calculator to degree mode, enter a bunch of fives (5555 or 55555555), take the reciprocal, take the sin, note similarity to pi. Very fun article.


While the trick is quite nice, I personally just press the "PI" button...


Calc's are funny.

Try 12345679 * 9x (where x < 10)


So what will happen? (tried on all my calc's and they gave the same result as http://www.google.com/search?q=12345679+*+92, which I think it's correct).


Try 123456789 * 9 * 2.


So what result should I be expecting? I'm getting a correct result on my Sharp EL-506W


12345679 * 9 * x where x is a single digit gives you nine copies of x.


> Try 123456789 * 9 * 2.

It's 12345679, not 123456789


Here is how to get e using a calculator:

sinh(1) + cosh(1)


pi / 180 = 0.01745 (a value commonly used for degree<->radian conversion). 1 / 180 = 0.0055555. That's the connection between the "magic" constants used in this trick.

It brings an older, simpler, not nearly as interesting calculator "trick" to mind: 11111111 * 11111111.


It brings an older, simpler, not nearly as interesting calculator "trick" to mind: 11111111 * 11111111.

  gnuplot> pr 11111111 * 11111111
  -2047269199
:-). For the intended result, people can put a '.' after one of the numbers to make it a double, or use a better calculator like bc or Python.


Much too highbrow for me.

39103 * 136

Then turn your calculator upside down and read the result.


Sure, but can anyone explain 5318008?


Walking upright shifted our focus away from butts?



Wow, I can't believe this made it to the top of Hacker News. Tranformation to Reddit complete!


Oh no.




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