# Thread: Triangle Circle Diameter (2k3)

1. ## Triangle Circle Diameter (2k3)

This is half excel half math help. If i have 1 side of an equilateral triangle - what is the easiest formula to put into excel that will give me the diameter of the circle using the 3 end points of the resultant triangle?

Thanks!

2. ## Re: Triangle Circle Diameter (2k3)

If you denote the side by s, a little elementary maths shows that the radius of the circle is s / (square root of 3), and the diameter is twice that: 2 * s / (square root of 3). So if you enter the side in cell A1, the formula

=2*A1/SQRT(3)

will return the diameter.

3. ## Re: Triangle Circle Diameter (2k3)

If A1 has the length:

=A1/COS(PI()/6)

(pi/6 = 30

4. ## Re: Triangle Circle Diameter (2k3)

I suppose even "easier" than both Hans and my equation is:

=1.1547*A1

if you are happy with 6 sig figs (the 1.1547 is actually 1.1547<font color=red>0</font color=red>, Of course you can simplify it further by reducing the sig figs accordingly(1.155*A1, 1.15*A1, 1.2*A1 or even just =A1 if you are happy with just 1 sig fig... <img src=/S/smile.gif border=0 alt=smile width=15 height=15>

Steve

5. ## Re: Triangle Circle Diameter (2k3)

And here is a picture...

6. ## Re: Triangle Circle Diameter (2k3)

Thanks Hans & Steve you've both made it clear as mud <img src=/S/laugh.gif border=0 alt=laugh width=15 height=15>

just kidding, thanks!

7. ## Re: Triangle Circle Diameter (2k3)

Here is my picture for the solution

Steve
PS cos(30

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