Question

What is pi and why do we need it

Answer 1

Answer:

See below

Step-by-step explanation:

π, pronounced as pi is the ratio between 2πr which is circumference to 2r which is diameter.

In word, π is circumference/diameter which has exact value of 3.14159... and it is also an irrational number too.

π is often used to be defined as 3, 3.14 or 22/7 [Keep in mind, these numbers are only approximation.] in some fields. In trigonometry, π is mostly used to refer as π radians or π rad which is equivalent to 180°.

Why do we need it? Because it’s useful in a field that requires rotation. If you notice, figure with circular base will always have π with it, the volume is an example.

In calculus, you need π to do solid of revolution method which is:

$\displaystyle \large{V =\pi \int\limits^a_b {[f(x)]^2} \ dx }\\\\\displaystyle \large{V = \pi \int\limits^a_b {[g(y)]^2} \ dy}$

In trigonometry, you need it for measurement/angle.  

So anything that’s related to revolution, rotation or related to circle must require π at least.

In general life, you do not use it but this is mostly applied in engineering field and anything related to science that involves with circle or revolve.

Let me know if you have any questions!