
A simple Solve gives me errors
Posted:
Apr 23, 2014 4:53 AM


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}]

