# What is $\pi$ in mathematics; does $\pi = 3.14$? From where does it come? [closed]

I faced one interview last week. In that interview, the interviewer asked a very basic question; but, it was out of my knowledge. He wanted to check my very basic mathematical skills, and wanted to see whether I am fond of mathematics or not.

The question was, what is pi?

The only thing I know of pi is that it equals $3.14$.

So, what is pi? From where this constant come? Why is the value $3.14$? As well as any other related questions that walk around this term "pi".

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In fact, pie is something delicious. For questions about the number $\pi$ (which does not equal $3.14$) cf. math.stackexchange.com/questions/400369/…, math.stackexchange.com/questions/53023/… o rsimply en.wikipedia.org/wiki/Pi –  Hagen von Eitzen Jun 8 '13 at 7:41
It is "PI" not "PIE" for the case the next time it rises as question in a written exam. –  al-Hwarizmi Jun 8 '13 at 8:03
None of the previous tags were appropriate. Jeez... –  Ｊ. Ｍ. Jun 9 '13 at 16:12

## closed as not a real question by fpqc, O.L., Jonas Meyer, Marc van Leeuwen, AmzotiJun 8 '13 at 7:59

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It is the ratio of a circle's circumference to its diameter. However it is an irrational number (i.e. if you sit down to list down all its digits you will have to go on and on) and is approximately equal to 3.14159.

Pi as continued fractions:

$$\pi = \cfrac{4}{1+\cfrac{1^{2}}{2+\cfrac{3^{2}}{2+\cfrac{5^{2}}{\ddots}}}}$$

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@shwawata: Did you make that picture? –  Jonas Meyer Jun 8 '13 at 8:07
@shaswata Thanks for explaining this. But I didn't understand this continued fraction. Can you explain me this, please ? –  devnull Jun 8 '13 at 9:53