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Thread: Diameter Of A Circle
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25th May 2014, 02:24 PM #46
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25th May 2014, 02:43 PM #47GOLD MEMBER
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25th May 2014, 02:48 PM #48
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26th May 2014, 09:22 AM #49GOLD MEMBER
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26th may and 0746am cst...and your still arguing about which way (if any) is the right way to come up with the correct answer
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26th May 2014, 01:18 PM #50
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27th May 2014, 12:34 AM #51
yes you're right, both method one and method two are equally easy to set out
Method 1 (polygon touching the outside of the circle) and method 2 (polygon touching the inside of the circle) is how people work out the value of pi to great precision -- the true value of pi lies between the perimeter of both polygons
but back to the OPI need to know the diameter of a circle that needs to be divided into 18mm sections, I attach a rough diagram to help illustrate what I am saying.
If someone can help me out and save me going mad from trying to figure it out I would be most appreciative.
Solution 1 — the circle is divided into an even number of 18mm chords and an 18mm hole is placed at the every second vertex (is that the correct name for the point where two chords meet?) The holes can be set out with compass and a pair of dividers.
Solution 2 — the circle is divided into an even number of 18mm arcs and a hole slightly less than 18mm in diameter is placed at every second arc intersect -- which results in the same outcome as Solution 1, but the holes are less than 18mm.
and Eskimo
because it's funregards from Alberta, Canada
ian
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27th May 2014, 02:20 AM #52
The answer I was thinking of, is to look at the two equations.
Solution 1. D = h/sin(pi/2n)
Solution 2. D = h/tan(pi/2n)
When the angle is small, sin(x) = x Also when the angle is small tan(x) = x
So the angle between segments is pi/2n, will get smaller as n gets larger, and sin(pi/2n) gets closer in value to tan(pi/2n)
Eventually all the solutions converge on the D = 2nh/pi which is the where you just measure along the arc.
Ray
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27th May 2014, 09:13 AM #53GOLD MEMBER
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not for the rest of us...we have NFI what your supposedly having fun with..if we knew we might be crapping on also.
But it is sad to see that a consensus as to which is correct method to arrive at correct answer has not been reached....how am i gunna work it out if you lot cant get it right...I wont be able to trust you
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27th May 2014, 12:24 PM #54GOLD MEMBER
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Hey its not our fault. Each of the answers are correct(or at least pretty close)......in the end it just depends on what question you think the OP is asking.
Of course I like my method better as (I think) it matches the drawing best(though really "bigger than XXX" isn't much of an answer lol). But it doesn't match his written question.
Stuart
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27th May 2014, 12:44 PM #55GOLD MEMBER
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I am still at a loss as to how one can have 4 different answers but yet they are all correct at the same time..oh yeah I forgot...roughenuff is goodenuff
I just hope the others are taking note should they wish to ever contemplate to get some precision machining carried out by you....is pretty close going to be good enough?
but ...you had a try at solving it..more than what I can do
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27th May 2014, 01:28 PM #56
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27th May 2014, 03:51 PM #57GOLD MEMBER
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