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Re: Problems solving using Solve
*To*: mathgroup at smc.vnet.net
*Subject*: [mg68829] Re: Problems solving using Solve
*From*: "akil" <akomur at wanadoo.nl>
*Date*: Sun, 20 Aug 2006 04:43:49 -0400 (EDT)
*References*: <ec65bn$1f8$1@smc.vnet.net>
*Sender*: owner-wri-mathgroup at wolfram.com
definition for cd is cd[input_,rcCD_,cx_,cy_] := rcCD*input + cy - rcCD*cx;
(which just defines a line of the form y=ax+b)
Using NSolve instead of Solve still takes way too long (quit it after 15
minutes, do not know if it even will solve it). I have about a 100 cones for
each part I need to test and the way it is now takes too long.
In my usage all values except beta and v are Reals. Beta is usually the
range [0, Pi/2] and v is also a Real.
For a solvable solution try:
{ax,ay}= {7,4} and {cx,cy}= {21,11} and
{centerOfMassx,centerOfMassy}={13,7} and rcAB=3 and
rcCD=7/4
That should give a solution, and quite fast at that.
Akil
"akil" <akomur at wanadoo.nl> schreef in bericht
news:ec65bn$1f8$1 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
>
>
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