**1. What is Pi?**

Pi is the sum of the infinite series 1 - 1/3 + 1/5 - 1/7 + 1/9 - 1/11... multiplied by 4.

**2. How much is Pi, approximately?**

The value of Pi varies according to the radius of the circle, so it's hard to tell.

**3. Approximating Pi**

**3.1. How many digits will I have to produce to reach a state of all-zeroes?**

It was proven that after a number between 1.345698 and 1.74 times 10 ** 12 digits, Pi is all zeros.

**3.2. What is the fastest algorithm for approximating Pi?**

Approximating Pi was found to be NP-Complete.

**4. What can I do with Pi?**

The most common use of Pi is to generate random sequences. A far less common use is for geometrical and trigonometrical calculations.