PI number (π): value, origin, how to calculate and what it is for

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Number Pi (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 all the way around a circle with a tape measure we get the measure of its perimeter. The diameter, in turn, is the measurement obtained from one end of this circle to the other.

Dividing the perimeter measurement by the diameter measurement, the result will be the number pi.

History

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.

Among the Babylonians and Egyptians calculations were found that approximated Pi. They already knew that the perimeter to diameter ratio was greater than 3.

But it was only in the 18th century that it became part of the mathematical symbols. The first to propose its use was the Welsh mathematician William Jones.

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The symbol (π) is a lowercase Greek letter, the first of the word περίμετρος, which means “perimeter” (in Portuguese).

It is called the Constant of Archimedes. This is because the mathematician Archimedes 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 value of Pi.

The number Pi is infinite. For this reason, it is represented with an ellipsis at the end. However, often only 3.1416 or 3.14 is used to facilitate mathematical calculations.

It should be noted that calculators limit the number of decimal places, as they do not fit as many places in them. The discovery of so many homes was made possible by computers.

Learn more about irrational numbers and the others numerical sets.

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 to calculate the lateral area of ​​the cylinder is:

THEthere = 2 π * r * h

Where,

THEthere: side area
π: Pi
r: lightning
H: height
Remembering that the height measurement is twice the radius, we have:

THEthere = 2 π * r * h
THEthere = 2 π * r2
THEthere = 2 π * 62
THEthere = 2 π * 36
THEthere = 72 * π
THEthere = 72 * 3,14
THEthere = 22.93 cm

Read too:

  • circle area
  • cone area
  • rectangle area
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