*To*: mathgroup@smc.vnet.net*Subject*: [mg11134] RE: [mg11082] Conic Sections and Quadric Surfaces*From*: "Barthelet, Luc" <lucb@ea.com>*Date*: Mon, 23 Feb 1998 21:40:52 -0500

you only have 5 points. you have a familly of conic sections that can go through those points: data = {{-1,0},{0,1},{2,2},{1,-1}, {0,-3}}; Show[Graphics[Point /@ data],AspectRatio->1,Axes->True] define the function, but assume a = 1 f[{x_,y_}]:= x^2 + b x y + c y^2 + d x + e y + f; sol = Solve[ f[#]==0& /@ data,{b,c,d,e,f}][[1]]; and you can plot it: << Graphics`ImplicitPlot` ImplicitPlot[f[{x,y}]==0 /. sol , {x,-2,3}] good luck! Luc. >-----Original Message----- >From: mavalosjr@aol.com [SMTP:mavalosjr@aol.com] To: mathgroup@smc.vnet.net >Sent: Wednesday, February 18, 1998 5:33 PM >To: mathgroup@smc.vnet.net >Subject: [mg11082] Conic Sections and Quadric Surfaces > >Dear Sir: >Ref: Introduction to Linear Algebra- 4th ed. Johnson,Riess and Arnold >(page 35) > >Find the equation of the conic section passing through the five points >(-1,0),(0,1),(2,2),(1,-1), (0,-3). Display the graph of the conic. > >When I try to set up the augmented matrix I get two (2) indeterminate >rows which >prevents my proceeding with the method outlined in the textbook Linear >Algebra with Mathematica by E. Johnson page 58 to 59. How can I get >around this?The equation to satisfy (an ellipse) is ax^2 + bxy + cy^2 + >dx + ey + f =0. Is there some other technique I can use to find the >equation given sevral points? >I am presently playing around with Fit[ data,{etc}] but I only know how >to fit quadratics. Thank you in advance. >Manuel Avalos >MAvalosjr@aol.com > > >