That should be an approximation. To get exactly pi the range of both integrals should be from minus infinity to infinity like this.
It’s the integral of the 2D Gaussian, which is fairly known.
According to JPL’s Chief Engineer for Mission Operations and Science, Marc Rayman-
Let's go to the largest size there is: the known universe. The radius of the universe is about 46 billion light years. Now let me ask (and answer!) a different question: How many digits of pi would we need to calculate the circumference of a circle with a radius of 46 billion light years to an accuracy equal to the diameter of a hydrogen atom, the simplest atom? It turns out that 37 decimal places (38 digits, including the number 3 to the left of the decimal point) would be quite sufficient.
Also the 2D gaussian integral is used to give an insight on why the 1D gaussian integral is sqrt of pi.
Here is a video with cool visualization for anyone interested.
That should be an approximation. To get exactly pi the range of both integrals should be from minus infinity to infinity like this. It’s the integral of the 2D Gaussian, which is fairly known.
The approximation is only around 4.28*10^-101 off from pi.
https://www.wolframalpha.com/input?i=integral+from+-a+to+a+of+(integral+from+-a+to+a+of+e^-(x^2%2By^2)dy)dx
https://www.wolframalpha.com/input?i=(1-erf(e^e)^2)*pi
And because it always bears repeating;
According to JPL’s Chief Engineer for Mission Operations and Science, Marc Rayman-
Let's go to the largest size there is: the known universe. The radius of the universe is about 46 billion light years. Now let me ask (and answer!) a different question: How many digits of pi would we need to calculate the circumference of a circle with a radius of 46 billion light years to an accuracy equal to the diameter of a hydrogen atom, the simplest atom? It turns out that 37 decimal places (38 digits, including the number 3 to the left of the decimal point) would be quite sufficient.Technically you need another 20 digits if you want to get down to a Planck length. (57 digits in total)
So the number 3 should be close enough for home use. Good to know. Thanks!
As an engineer, I approve this message!
My maths exam asked me to consider pi=5.
“I will… consider it.”
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Ah, you’re right. I was thrown off by WolframAlpha saying the integral = π ≈ 3.1416 Both of those should be ≈
(x^2 + y^2)=1 is the equation for a unit circle, so it’s definitely related. Just not quite how I thought.
Also the 2D gaussian integral is used to give an insight on why the 1D gaussian integral is sqrt of pi. Here is a video with cool visualization for anyone interested.
“Fix” it with
Lim as eee-> infinity(where eee is some other e-named variable)