Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!lll-winken!elroy.jpl.nasa.gov!sdd.hp.com!caen!uwm.edu!bionet!agate!shelby!cascade.stanford.edu!dolores!bob From: bob@dolores.Stanford.EDU (Bob Lodenkamper) Newsgroups: comp.sys.handhelds Subject: Re: Bug in QUAD Message-ID: Date: 1 Mar 91 03:54:09 GMT References: <89355@tut.cis.ohio-state.edu> Sender: news@cascade.Stanford.EDU (USENET News System) Organization: Center for Integrated Systems, Stanford University Lines: 28 In-Reply-To: adkins@tortoise.cis.ohio-state.edu's message of 28 Feb 91 22:45:11 GMT In article <89355@tut.cis.ohio-state.edu> adkins@tortoise.cis.ohio-state.edu (Brian Adkins) writes: I've discovered a possible bug in the QUAD function. Consider the equation: x^2 ----------- = .58 QUAD returns 'x=s1*76.15.../5000' neither one of these (.02 - x)^2 roots is correct. If the equation is re-written as x^2 = .58*(.02 - x)^2 it works fine. HP tech support said it looked like it wasn't working "very well" and to call back in 6 months to see if anything was done! I have revision E. My opinion is that it not only doesn't work very well in this case, but it just doesn't work. Any other ideas? My fearless guess is that QUAD will only work if the equation is in a polynomial format. If a quadratic is expressed as a rational function, trignometric mess, whatever, the 48 merrily expands to second order and solves the resulting polynomial. This is what happens, according to the manual, should one attempt to use QUAD to solve tan(x) = x. If this is correct, the behavior you describe is precisely what one would expect - after all, how can the 48 be expected to recognize all algebraic messes that are quadratics? I'd be happy if it could, but then again I want symbolic integration, a special function library and other goodies that I'll have to wait 5 or 10 years for. - Bob