---- START NEW MESSAGE --- Received: from cherry.ease.lsoft.com [209.119.0.109] by dpmail10.doteasy.com with ESMTP (SMTPD32-8.05) id A708B050200; Tue, 27 Jan 2004 17:57:28 -0800 Received: from PEAR.EASE.LSOFT.COM (209.119.0.19) by cherry.ease.lsoft.com (LSMTP for Digital Unix v1.1b) with SMTP id <20.00CBFEC8@cherry.ease.lsoft.com>; Tue, 27 Jan 2004 20:57:22 -0500 Received: from MITVMA.MIT.EDU by MITVMA.MIT.EDU (LISTSERV-TCP/IP release 1.8e) with spool id 7836 for PICLIST@MITVMA.MIT.EDU; Tue, 27 Jan 2004 20:57:16 -0500 Received: from MITVMA (NJE origin SMTP@MITVMA) by MITVMA.MIT.EDU (LMail V1.2d/1.8d) with BSMTP id 3341; Tue, 27 Jan 2004 20:55:22 -0500 Received: from mailhub1.otago.ac.nz [139.80.64.218] by mitvma.mit.edu (IBM VM SMTP Level 430) via TCP with ESMTP ; Tue, 27 Jan 2004 20:55:21 EST X-Comment: mitvma.mit.edu: Mail was sent by mailhub1.otago.ac.nz Received: (from root@localhost) by mailhub1.otago.ac.nz (8.12.9/8.12.9) id i0S1tJbH012202; Wed, 28 Jan 2004 14:55:19 +1300 Received: from physics.otago.ac.nz (mail.physics.otago.ac.nz [139.80.80.35]) by mailhub1.otago.ac.nz (8.12.9/8.12.9) with ESMTP id i0S1tIXt012163; Wed, 28 Jan 2004 14:55:19 +1300 Received: from 192.168.1.101 (electronx.otago.ac.nz [139.80.30.4]) by physics.otago.ac.nz (8.11.6/8.11.6) with ESMTP id i0S1tIP32623; Wed, 28 Jan 2004 14:55:18 +1300 User-Agent: KMail/1.5.4 References: <001301c3e53f$ad6ce0c0$0100a8c0@carlos98> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-scanner: scanned by Inflex 1.0.12.7 Message-ID: <200401281455.17651.royward@physics.otago.ac.nz> Date: Wed, 28 Jan 2004 14:55:17 +1300 Reply-To: pic microcontroller discussion list Sender: pic microcontroller discussion list From: Roy Ward Subject: Re: [OT:] Curves intersection Comments: To: Carlos Marcano To: PICLIST@MITVMA.MIT.EDU In-Reply-To: <001301c3e53f$ad6ce0c0$0100a8c0@carlos98> Precedence: list X-RCPT-TO: Status: U X-UIDL: 371856008 On Wednesday 28 January 2004 14:34, Carlos Marcano wrote: > Hi all: > > I got to admit that I am struggling with something that I should know = as > an engineer. I need to find analitically the points of intersection of two > curves, that is: > > I) y=3D 1-(x*x) > > II) y=3D sen(x) I assume that you mean y=3Dsin(x) > Normally that would be as simple as doing I=3DII and resolving but in this > case the fact that II is a trigonometrical ecuation brings some issues to > the resolution. Having 1 - (x*x) =3D sen(x) I can=B4t find a way to get = the > posible values for x. I could try a graphical solution but I want the > analitical (i.e. numerical) solution. Any ideas? I'm pretty sure there isn't an analytical (btw, analytical !=3D numerical)= =20 solution to this, not of the form x=3D(some combination of basic functions). y=3D(some combination of basic functions). I'd suggest a numerical approach, such as bisection (or something that=20 converges a little faster) to get a number with whatever accuracy you want. Try to find the zero crossing point of 1-x*x-sin(x) in whatever region you= =20 want (there will be more than one solution, one positive, one negative I=20 think). Cheers, Roy Ward. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads .