The math behind a neat calculator trick (divisbyzero.com)

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.

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.

  gnuplot> pr 11111111 * 11111111
  -2047269199

Sure, but can anyone explain 5318008?

Calc's are funny.

Try 12345679 * 9x (where x < 10)

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

Much too highbrow for me.

39103 * 136

Then turn your calculator upside down and read the result.

Here is how to get e using a calculator:

sinh(1) + cosh(1)