Be Excellent To Each Other

OK, so I need MATHS to illustrate something I am working on. Basically the difference in circumference (or perimeter) in square and round needles of equivalent size when measured through a standard needle gauge (which is given in mm diameter) so the widest point of each will be the diameter of the round needle and the diagonal of the square needle (being the widest point).

I'm pretty sure the maths is sound, what I really am not sure of is if I have rendered the calculation properly: I've basically forgotten how to write simple equations.



Is that right? Specifically the second.

The second is right, but not how I'd have done it (4 * 8 * cos (45deg)) = 22.6274

Ah, fair enough, but at least that shows it is right. I was pretty certain the result was right and I think everyone knows Pythagoras at least. What I wasn't sure of was if I'd actually written the equation properly (I know I don't need the multiplication symbol in there, but thought it made it clearer to those of us who have forgotten how maths works

I know it's is semantics but it looks really.wrong to write the circumference like that instead of 2πr.

Besides that, would showing the (larger) difference in area not be more useful?

Though 2πr is correct and absolutely the standard form, a needle gauge when working with round needles measures the diameter, so to make this representative in the calculation as displayed I'd have to halve the diameter to give the radius to then multiply again to fit the form, which doesn't make any sense.



Not for what I am using it for. Yarn wraps around the diameter or perimeter of the needle, rather than occupy the space within it, so it is the difference in the distance the yarn has to travel around the needle that has to be accounted for when sizing the needle for the task.

Oh yeah, there's another kind of needle than the ones I get stabbed by.

I can stop being freaked out by the possibility of someone using a square one now.

I'd be freaked out, too, if someone stuck a needle in me that had an 8mm diameter!

That too I guess! The venesection one is about 2mm and that's quite enough.

2mm? Goodness, that is a hefty bit of metalware I'm sorry to hear that