User talk:Kovac Jozef

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Hello, Kovac Jozef, and welcome to Wikipedia! Thank you for your contributions. I hope you like the place and decide to stay. Here are some pages that you might find helpful: I hope you enjoy editing here and being a Wikipedian! Please sign your messages on talk pages using four tildes ( ~ ); this will automatically insert your username and the date. If you need help, check out Questions, ask me on my talk page, or ask your question on this page and then place  before the question. Again, welcome! Dmcq (talk) 19:59, 9 March 2012 (UTC)
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Angle trisection
Wikipedia requires citations in WP:Reliable sources backing up things which seem improbable, like solutions of problems which hae been proven impossible. Uncited discoveries are counted as an editors own WP:Original research which is not allowed in Wikipedia. Dmcq (talk) 19:59, 9 March 2012 (UTC)


 * Incidentally, it's easy to check by the law of cosines that the angle AOC you construct satisfies cos AOC = 17/18, while cos 20 degrees is not rational. (In fact, AOC has measure about 19.188... degrees.)  --Joel B. Lewis (talk) 03:08, 10 March 2012 (UTC)

Jozef Kovac my response is: Calculating arc length and chord of circle using equations found on Wikipedia page http://en.wikipedia.org/wiki/Circular_segment Wikipedia: The arc length s of 20 degree angle with radius R = 3 is: ·	s = a / 180 x pi x R = 20 /180 x p x R = 1.11… x 3.141… x 3 = 1.04719… there is no mistake here!!! Calculations of arc length of 20 degree angle with radius R = 3 from my contribution ·	L1 = 2 x pi x R = 18.8495... ·	20 degree arc length L1/18 = 18.8495.../18 = 1.047197…      same number there is no mistake here!!! Wikipedia: The chord length of 20 degree angle with radius R = 3 is: ·	c = 2 R sin a/2 = 2 x 3 x sin 20/2 = 6 x sin 10 = 6 x 0.1736… = 1.04188… Wikipedia: Using the cosine law Joel B. Lewis cites, calculating the chord length of 20 degree angle with radius R = a = b = 3 is: ·	c2 = a2 + b2 – 2ab cos c = 9 + 9 – 2 x 3 x 3 x cos 20 = 18 – 18 x 0.9396… = ·	= 18 – 16.9144… = 1.0855… ·	c2 = 1.0855… taking a square root  c = 1.04188… The cord length is slightly shorter than the arc length as can be expected.

??????????????????                  Joel B. Lewis (In fact, AOC has measure about 19.188... degrees.)???? Dear Mr.Joel B. Lewis can you please show how you arrived to 19.188... angle? Because the arc length of 19.188...degrees = a / 180 x pi x R = 19.188.../180 x p x R = 1.00468... cord length of 19.188...degrees using cosine law c2 = a2 + b2 – 2ab cos 19.188...= 18 - 17.000 = 1.000... cord length of 19.188...degrees using equation c = 2 R sin a/2 = 2 x 3 x sin 19.188.../2 = 6 x sin 9.55... = 0.9999....


 * Segment CR3 is a chord of length 1 in the circle of radius 3 centered at O. As you note above, if angle AOC (= angle R3OC) were a 20 degree angle, this chord should instead have length 1.04188….  This makes it clear that the angle you've constructed does not have measure 20 degrees.
 * As for how to compute the measure of this angle: applying the Law of Cosines in triangle R3OC at angle R3OC, we have 12 = 32 + 32 - 2 * 3 * 3 * cos(m R3OC). Solving this equation for the cosine term gives cos(m R3OC) = 17/18.  Now apply the arccosine to get the angle measure.
 * --Joel B. Lewis (talk) 21:43, 15 May 2012 (UTC)