What is Pi - sciencenerds

What is 𝛑?

Let's assume, we are asked to draw a circle of radius three centimetres. So we draw a circle like this. The length of the red line will be the perimeter. And we have a special name for the perimeter of a circle. It's called the circumference. This length will be the circumference. This length will measure 18.85 centimetres. The next thing we need to find out is the diameter of the circle. The radius of any circle is half of its diameter. Hence, the diameter will be 2 multiplied by 3, which equals 6 centimetres. 

Now we've been asked to draw a circle of radius four centimetres. It will be slightly bigger than the previous one. This red boundary will be the circumference. This time too we measure the circumference. For this circle, we get the circumference as,25.1 Centimeters. And the Diameter will be twice its radius, which equals  8 centimetres. We looked at two different cases here. 

One circle with 3 as the radius, and another with 4 as its radius. 

In both cases, we calculated the circumference and the diameter. Let's zoom out and find the ratio of the circumference by diameter in each case. On calculating the value of circumference by diameter in the first case, we will approximately get it as  3.14 And guess what! In the second case too we get the value of circumference upon diameter as approximately 3.14.

No matter which circle you take into consideration, the value of circumference by diameter will always be approximately equal to 3.14. This value is Pi. Remember, both these values are approximations. Now let's zoom out and deduce a formula for the circumference. As the circumference by diameter equals Pi, we can say that the circumference of a circle equals Pi multiplied by the Diameter. If we call the diameter 'D' then the formula can be written as multiplied by D'.Which can also be written as 'Pi multiplied by 2R'.

i.e circumference = 2𝛑R = 𝛑D

Because the diameter is twice the radius. So the circumference of a circle is written as 2𝛑R. It's an important formula, as it gives we can calculate the circumference even if you just have the radius of the circle. 

There's another important thing about this special Constant 𝛑 (Pi). We get the same value when we divide 22 by 7. So the value of 𝛑 approximately equals 3.14 or  22 by 7. But why do we use this symbol for Pi? What is this symbol? 

𝛑 is actually the 16th letter of the Greek alphabet. But the question remains the same, why the 16th letter? We just saw that 𝛑 has got something to do with the perimeter or the circumference of the circle. Let's use Google Translate to see the Greek equivalent of the perimeter. 

As we can see the first letter of the Greek word is 𝛑. 

Let's try a couple of more words related to the perimeter. How about the periphery? 

The first letter is still Pi. Hmm. Okay, let's try circumference.

 As we can see the first letter is still 𝛑. That's probably why this symbol was used to denote Pi. Anyway, don't forget an important point. Pi is the result of the circumference of the circle, divided by its diameter. So it is the ratio of the circumference to the diameter. Based on the formula if the diameter of the circle is 1 unit. Then its circumference will be Pi units. If we have a circle with a diameter equal to n unit, then the length of its boundary will be n times Pi(n𝛑) or approximately 3.14 units.


~sciencefreak