Pi number (π) is an irrational number whose value is 3.14159265358979323846…, that is, an infinite sequence of digits.
How to calculate?
Pi results from dividing the perimeter by the diameter of a circle (π = perimeter / diameter) .
If we measure the entire circumference of a circle with a tape measure we obtain the measurement of its perimeter. The diameter, in turn, is the measurement obtained from one end of the circle to the other.
Dividing the perimeter measurement by the diameter measurement, the result will be the number pi.
Story
Studied since antiquity, as shown by historical records, the number pi continues to pique the curiosity of scholars. The reason is that its calculation results in trillions of decimal places.
Between Babylonians and Egyptians, calculations were found that approached Pi. They already knew that the ratio between the perimeter and the diameter was greater than 3.
But it was only in the 18th century that it became part of mathematical symbols. The first to propose its use was the Welsh mathematician William Jones.
The symbol (π) is a lowercase Greek letter, the first in the word περίμετρος , which means “perimeter” (in Portuguese).
It is called the Archimedes Constant. That’s because the mathematician Arquimedes was the first person to calculate and obtain the ratio between the perimeter and the diameter.
But after Archimedes, the scientist Ptolemy managed to get even closer to the Pi value.
The number Pi is infinite. For this reason, it is represented with an ellipsis at the end. However, only 3.1416, or 3.14, is often used to facilitate mathematical calculations.
It should be noted that the calculators limit the number of decimal places, as there are not enough places in them. The discovery of so many houses was made possible thanks to computers.
What is it for?
Let’s look at an example.
Calculate the area of the side of a cylinder whose radius is 6 cm.
The formula for calculating the lateral area of the cylinder is:
A l = 2 π * r * h
Where,
A l : lateral area
π : Pi
r : radius
h : height
Remembering that the height measurement is twice the radius, we have:
A l = 2 π * r * h
A l = 2 π * r 2
A l = 2 π * 6 2
A l = 2 π * 36
A l = 72 * π
A l = 72 * 3.14
A l = 22 , 93 cm