ELI5: Explain Like I'm 5

Leibniz formula for π

Okay kiddo, let me try to explain the Leibniz formula for pi in a way that's easy for you to understand!

First things first, do you know what pi is? Pi is a special number that helps us figure out the size of circles. It's kind of like a secret code that helps us figure out the distance around a circle (we call that the "circumference") if we know how big the circle is across (we call that the "diameter"). Pi is always the same number, no matter how big or small the circle is, and we write it as 3.14159265359... (but it goes on forever!)

Now, the Leibniz formula is a way to figure out pi using math. It looks like this:

π = 4/1 - 4/3 + 4/5 - 4/7 + 4/9 - 4/11 + 4/13 - 4/15 + ...

That might look kind of confusing, but don't worry! Here's what it means in simpler terms:

- The formula is a pattern that tells us how to add up a bunch of fractions.
- Each fraction in the pattern has 4 on top and a different number on the bottom (that's what the little numbers under the line mean).
- The pattern keeps going on forever, with a plus sign or a minus sign alternating between each fraction.

Now here comes the tricky part - how does this formula actually help us figure out pi? Well, it turns out that if we keep adding up more and more fractions from the pattern, we get closer and closer to the value of pi!

For example, if we add up the first 4 fractions in the pattern (4/1 - 4/3 + 4/5 - 4/7), we get a number that's pretty close to pi (it's around 3.14). But if we add up the first 400 fractions, we get even closer to pi (it's around 3.1415). And if we add up the first 4,000 fractions, we get super duper close to pi (it's around 3.1415927)!

So that's how the Leibniz formula helps us figure out pi - by using a special pattern of fractions that gets us closer and closer to the real value of pi. Pretty neat, huh?