"It is absolutely paradoxical; we cannot understand it, and we don't know what it means, but we have proved it, and therefore we know it must be the truth."
-Benjamin Peirce, American 19th Century mathematician on href="http://en.wikipedia.org/wiki/Euler%27s_identity">Euler's Identity
e^(i*pi)+1 = 0
I was reminded of Euler's Identity when SMBC took on "Polish Hand Magic" The comic gives a quick example of how to multiply using your fingers and then a proof of why it works, and then mocks how... insufficient that explanation is.
Similarly here's another unfulfilling explanation of the Euler Identity.
I did get a kick out of this bit: A mathematical joke asks, "How many mathematicians does it take to change a light bulb?" and answers "-e^(ipi)" (which, of course, equals 1).