RE: Problems solving using Solve

*To*: mathgroup at smc.vnet.net*Subject*: [mg68822] RE: [mg68809] Problems solving using Solve*From*: "David Park" <djmp at earthlink.net>*Date*: Sun, 20 Aug 2006 04:43:40 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Akil, Don't do so much in one step. When I plug your data into Cone there are already problems. First make certain that the Cone routine is working and giving you what you expect. If it isn't you could add Print statments in Cone to see what is happening. Also, I would calculate afg and look at it before plugging into the last Solve statement. Also, are you expecting afg to be calculated entirely symbolically? If you define the data including centerOfMassy, then you couldn't differentiate with respect to centerOfMassy. If you have a problem you have to go back and make certain that each step is working before putting it all together. David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: akil [mailto:akomur at wanadoo.nl] To: mathgroup at smc.vnet.net I have a problem suing the following code: Cone[beta_, v_,rcAB_,rcCD_,ax_,ay_,cx_,cy_,centerOfMassx_,centerOfMassy_] := Module[ {betaUsed, vtemp, fx, fy, ex, ey, waarde,criticalRC,criticalHeight,xVerplaatsing,ePx2Py2}, betaUsed = beta ; vtemp = v; fline[x_] := Tan[betaUsed]x - Tan[betaUsed]vtemp; fx = x /. Solve[fline[x] == cd[x,rcCD,cx,cy], x][[1]]; fy = cd[fx,rcCD,cx,cy]; criticalRC = (centerOfMassy - fy)/(centerOfMassx - fx); criticalHeight = -criticalRC*fx + fy; ex = (-ay + rcAB*ax + criticalHeight)/(rcAB + (-criticalRC)); ey = ab[ex,rcAB,ax,ay]; xVerplaatsing = ex - vtemp; ePx2Py2 = Sqrt[xVerplaatsing^2 + ey^2]; waarde = xVerplaatsing/ePx2Py2; ArcCos[-waarde] ]; afg = Simplify[D[Cone[beta,v,rcAB,rcCD,ax,ay,cx,cy,centerOfMassx,centerOfMassy],v] , TimeConstraint -> 1 ]; Solve[afg== 0, v]; eg. {ax,ay}= {-44.9376, 36.1678} and {cx,cy}= {17.8329, 122.477} and {centerOfMassx,centerOfMassy}={-18.6338,72.3356} and rcAB=-0.166667 and rcCD=-0.37931 Doing the Solve[afg== 0, v] takes ages (after an hour I quit it). Is there any way I can make it work faster? Is any code in Cone such that it unnecessarily makes it run faster? So are there any ways I can try to make everything run faster? Using integers it runs, but it takes too long when using real cones (made up of four points A B C D and a centerOfMass). Akil