Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ ¹ ² ³ °
 

You are not logged in. #1 20140128 19:58:21
4 secants circle geometryLet ABCD be a cyclic quadrilateral. Let P be the intersection of \overline{AD} and \overline{BC}, and let Q be the intersection of \overline{AB} and \overline{CD}. Prove that the angle bisectors of \angle DPC and \angle AQD are perpendicular. Batman shows Superman his new phone. Batman"Alfred, whats the temperature in London?" Alfred"Just a second, sir." Alfred turns on his iPhone."Siri, whats the temperature in London?" Siri  "Six centigrade." Alfred"Six centigrade sir." Batman"See?" #2 20140128 22:01:14
Re: 4 secants circle geometryHi; In mathematics, you don't understand things. You just get used to them. I have the result, but I do not yet know how to get it. All physicists, and a good many quite respectable mathematicians are contemptuous about proof. #3 20140128 23:02:00
Re: 4 secants circle geometryhi thedarktiger, Last edited by bob bundy (20140128 23:02:42) You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei #4 20140129 01:17:48
Re: 4 secants circle geometryHi, "The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do."  Ted Nelson #5 20140129 18:51:05
Re: 4 secants circle geometrywow! thanks! @bob bundy, you are really good at geometry. phrostister and bobym, thanks for the pics! Batman shows Superman his new phone. Batman"Alfred, whats the temperature in London?" Alfred"Just a second, sir." Alfred turns on his iPhone."Siri, whats the temperature in London?" Siri  "Six centigrade." Alfred"Six centigrade sir." Batman"See?" #6 20140130 00:35:06
Re: 4 secants circle geometryHere is a little video of post #4, demonstrating the perpendicular property of the two bisectors in various cyclic quadrilateral shapes. Done in Geogebra by randomly dragging the points of the quadrilateral along the curve of the circle. Last edited by phrontister (20140130 22:44:45) "The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do."  Ted Nelson #7 20140203 20:54:57
Re: 4 secants circle geometrythanks a lot for the video! So I guess they are always perpendicular. Last edited by thedarktiger (20140203 20:56:00) Batman shows Superman his new phone. Batman"Alfred, whats the temperature in London?" Alfred"Just a second, sir." Alfred turns on his iPhone."Siri, whats the temperature in London?" Siri  "Six centigrade." Alfred"Six centigrade sir." Batman"See?" 