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Re: A simple Solve gives me errors
Posted:
Apr 24, 2014 4:02 AM


In the definitions of eq1 and eq2, ":=", which means SetDelayed, should be "==" (double equals sign), which means Equal and is used to form equations.
On Apr 23, 2014, at 4:54 AM, Ste[hen Gray <stevebg@roadrunner.com> wrote:
> I want to find the center C of a circle in 3D where the plane is defined > by points p1,p2,p3. I wrote this: > > p1 = {p1x, p1y, p1z}; (* tell it that p1,p2,p3 are vectors *) > p2 = {p2x, p2y, p2z}; (* center of circle ctr = f p1+g = p2+(1fg)p3 *) > p3 = {p3x, p3y, p3z}; (* keep the center in the plane of p1,p2,p3 *) > > ctr = f p1 + g p2 + (1  f  g) p3; > eq1 = (ctr  p1).(ctr  p1)  (ctr  p2).(ctr  p2) := 0; > eq2 = (ctr  p1).(ctr  p1)  (ctr  p3).(ctr  p3) := 0; > > I get errors of a type I've seen before: > > SetDelayed::write: Tag Norm in Norm[{p1x+f p1x+g p2x+(1fg) p3x,p1y+f > p1y+g p2y+(1fg) p3y,p1z+f p1z+g p2z+(1fg) p3z}] is Protected. >> > > And a similar one. I don't know what to do about this. > I want to do > Solve[{eq1, eq2}, {f, g}] >
Murray Eisenberg murray@math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 240 2467240 (H) University of Massachusetts 710 North Pleasant Street Amherst, MA 010039305



