Graph of c=2πr

[Clanscorpia]

So I just made a graph of c=2 π r for practice and to check I did it in wolfram alpha but it showed the graph continued into the negatives. How can this work if its the circumference of a circle? Or is it just Wolfram Alpha not recognizing the forumla and my graph starting at [6.28, 1] correct

[paps511]

C=2 pi r is just a line with slope of 6.28.

 

Are you trying to graph a circle?

[corrado33]

Sorry, no. 2(Pi)r is the circumference of the circle. To wolfram (or any other graphing program) it's a simple line relating c with r since 2 and Pi are constants. The graphing program doesn't know what artificial limits you put on that value (aka the circumference is generally not negative.) 

 

The only thing graphing that tells you is that there is a linear relationship between the circumference of a circle and the diameter of the same circle (2r is the diameter.) 

[Cryosec]

I think wolfram alpha is considering the equation like a y = 2πx, where 2π is the angular coefficient of the line

[Sauron]

You're just working out how long the circumference is for each value of r, if r is negative the formula will give a negative. To make it more realistic (a circumference can't be negative) you must use the absolute value: c=|2πr|

[Clanscorpia]

1 minute ago, paps511 said:

C=2 pi r is just a line with slope of 6.28.

 

Are you trying to graph a circle?

No I know how to do it. just x^2+y^2=z. I m just wondering why it gave the result it did

[corrado33]

2 minutes ago, paps511 said:

C=2 pi r is just a line with slope of 6.28.

 

Are you trying to graph a circle?

I think the OP is confused because it gives negative values, and circumferences are not really ever reported as negative.