**Pi Approximation Day:** Pi Approximation Day is observed on 22 July reach year to celebrate the usage of the mathematical constant π (pi).

**Key Highlights:**

- Pi Approximation Day is also known as Casual Pi Day.
- The value of Pi is 3.14, which is a result of the fraction 22/7 – the date.
- However, some people also celebrate the Pi Approximation Day on 14 March, as the simplified value of the fraction is 3.14, which turns to be 14/3 in the date format.

**Significance:**

- Pi plays a significant role in the calculation of the circumference of a circle and even NASA uses it for calculating spacecraft trajectories. The value of Pi is 22/7 or 3.14, which makes the number constant and an irrational number.
- Pi is used in several mathematical problems consisting of the lengths of arcs or other surfaces like the areas of ellipses, sectors, and other curved surfaces, and the volumes of various solids.
- Pi is also used in several formulas of physics and engineering to describe such periodic phenomena as the motion of pendulums, the vibrations of strings, and alternating electric currents.

**Note: The legendary Indian Mathematician Srinivasa Ramanujan early in the 20th century developed exceptionally efficient ways of calculating Pi and was later incorporated into computer algorithms.**

**History of Pi Approximation day:**

- The importance of Pi was recognized 4000 years ago.
- Babylonians used approximated values of Pi to calculate the dimensions of circles. It’s indicated by the Rhind papyrus that ancient Egyptians used a value of 256/81 or about 3.16045.
- Archimedes of Syracuse (287–212 BC), one of the greatest mathematicians of the ancient world, in 250 B.C. was the first person to do the calculation of π.
- Archimedes tried to show that the value π is between 3 1/7 and 3 10/71.
- Pi is sometimes referred to as the ‘Archimedes’ Constant.’
- It is dedicated to the infinite constant.

**Pi Approximation Day depends upon the format of the Date:**

- Pi Approximation day is observed annually to celebrate the usage of the mathematical constant π (pi).
- Pie day is observed on March 14 and Pi Approximation Day is observed on July 22.
- Pie day was founded by Larry Shaw in the year 1988 at the San Fransisco Exploratorium, USA.
**Note: The day also marks the birth anniversary of Albert Einstein.**- In November 2019 United Nations designated Pi day as the International Day of Mathematics.

**What is Pi (π)?**

- Pi (π) is defined as the ratio of the circumference of a circle divided by the distance across the circle, i.e., the diameter of the circle.
- The value of Pi is 22/7 or 3.14.
- It is an irrational number, which implies that it is not possible to calculate Pi by dividing an integer by some other integer.
- Pi is an endless and never-repeating number.
- The most exact calculation of Pi is to ten trillion digits.

**Few More Important Facts About Pi:**

- π symbol was devised by British mathematician William Jones in 1706 to represent the ratio and later it was popularized by the Swiss mathematician Leonhard Euler.
- The number π (/paɪ/) is a mathematical constant.
- It is defined as the ratio of a circle’s circumference to its diameter
- It is approximately equal to 3.14159.
- It is also referred to as Archimedes’ constant.
- Fractions such as 22/7 are commonly used to approximate it.
- Its decimal representation never ends and never settles into a permanently repeating pattern.
- It is known that π is a transcendental number:
- There is no zero in the first 31 digits of Pi
- At position 763 which is also known as Feynman Point, there are six nines in a row
- Johann Lambert proved Pi is irrational in 1768
- As the exact value of pi cannot be calculated, we can never find the accurate area or circumference of a circle.
- The Welsh mathematician William Jones began using the symbol for pi in 1706.

**Fun Fact:**

In 2005, Lu Chao of China recited 67,890 digits of pi.

In 2015, Suresh Kumar Sharma, a former vegetable vendor from Jaipur, India now a memory coach, set a world record when he successfully recited more than 70,030 digits of pi. It took 17 hours to complete the memorization.