217: e to the pi Minus pi
|e to the pi Minus pi|
Title text: Also, I hear the 4th root of (9^2 + 19^2/22) is pi.
e is a mathematical constant roughly equal to 2.71828182846. π is another, roughly equal to 3.14159265359. Both are transcendental numbers.
The first panel discusses eπ - π, which is around 19.999099979 — very close to 20. Black Hat explains how he tricked a programming team into believing that eπ - π is exactly 20, and that if the system they were building didn't agree, there were errors in the code. This made them waste a lot of time trying to find a nonexistent bug until they realized that Black Hat was lying.
Floating point numbers are how computers store real numbers — or rather, approximate them: a true real number requires infinite amounts of data to represent. The "floating-point handlers" would be the code performing the eπ - π calculation.
Some random facts about the math here:
- eπ - π is an irrational number, but this is not a trivial fact. It was proven by Yuri Valentinovich Nesterenko in the late 20th century.
- The mysterious almost-equation is believed to be a mathematical coincidence, or a numerical relationship that "just happens" with no satisfactory explanation. It can be rearranged to (π + 20)i ≈ -i, so cos(ln(π + 20)) ≈ -1. Piling on a few more cosines gives cos(π cos(π cos(ln(π + 20)))) ≈ -1, which is off by less than 10−35!
The title text pokes fun at another coincidence: ∜(9² + 19²/22) ≈ 3.1415926525, close to π. The humor comes from the fact that π is meant to be transcendental. Transcendental numbers are numbers that cannot be expressed through basic arithmetic with integers; one cannot end up with the exact value for any transcendental number (including π) by adding, subtracting, multiplying, dividing, exponentiating and/or taking the nth root of any whole number.
A much later comic, 1047: Approximations, puts forth quite a few more mathematical coincidences.
- Cueball: Hey, check it out: e^pi-pi is 19.999099979. That's weird.
- Black Hat: Yeah. That's how I got kicked out of the ACM in college.
- Cueball: ...what?
- Black Hat: During a competition, I told the programmers on our team that e^pi-pi was a standard test of floating-point handlers--it would come out to 20 unless they had rounding errors.
- Cueball: That's awful.
- Black Hat: Yeah, they dug through half their algorithms looking for the bug before they figured it out.
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