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Thread: Triangle Circle Diameter (2k3)

20070717, 14:54 #1
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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!<img src=/w3timages/blueline.gif width=33% height=2>
<big>John</big>

20070717, 15:14 #2
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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.

20070717, 15:15 #3
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Re: Triangle Circle Diameter (2k3)
If A1 has the length:
=A1/COS(PI()/6)
(pi/6 = 30

20070717, 15:26 #4
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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

20070717, 15:32 #5
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Re: Triangle Circle Diameter (2k3)
And here is a picture...

20070717, 17:53 #6
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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!<img src=/w3timages/blueline.gif width=33% height=2>
<big>John</big>

20070717, 19:27 #7
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Re: Triangle Circle Diameter (2k3)
Here is my picture for the solution
Steve
PS cos(30