Re: ImplicitPlot errors

*To*: mathgroup at smc.vnet.net*Subject*: [mg75094] Re: [mg75066] ImplicitPlot errors*From*: anguzman at ing.uchile.cl*Date*: Mon, 16 Apr 2007 20:19:39 -0400 (EDT)*References*: <200704160811.EAA09682@smc.vnet.net>

Hello: I'm using Mathematica v5 and I'm not having problems ImplicitPlot[{x^2 + x*y + y^2 == 7, y == 2 Sqrt[7/3]}, {x, -5, 5}] It plots an inclined ellipse and an horizontal tangent line. I suspect it's because you've defined "y" before, so Mathematica uses this value in the first equation and doesn't see the other variable it needs. Type Clear[y]; and the execute the plotting. This should work. The other thing you could do is using variable "y" in a local enviroment with Block or Module.. Hope this helps However, I do get your error message when I try to plot with respect to y {y,-5,5}. I guess because is because equation y==2 sqrt[7/3] doesn't have a distinct (other than y) variable. Atte. Andres Guzman David Rees <w3bdevilREMOVE at THISw3bdevil.com> ha escrito: > Hi, > > I've been trying to get ImplicitPlot to plot an implicit function (naturally > ;) ), but it throws errors to cryptic for me, even when copying and pasting > from the Mathematica function reference. > > In[40]:= ImplicitPlot[{x^2 + x*y + y^2 == 7, y == 2*Sqrt[7/3]}, {x, -5, 5}] > > ImplicitPlot::var : > > Equation x^2+x > Function[x,x^2+2xy-3y^2-16]+Function[x,x^2+2xy-3<<1>>-16]^2==7 does not have > a single variable other than x > > ImplicitPlot::var : > > Equation Function[x,x^2+2xy-3y^2-16]==2Sqrt(7/3) does not have a single > variable other than x > > Out[40]:=\!\(ImplicitPlot[{x\^2 + x\ Function[x, x\^2 + 2\ > xy - 3\ y\^2 - 16] + Function[ > x, x\^2 + 2\ xy - 3\ y\^2 - 16]\^2 == 7, Function[x, x\^2 + 2\ > xy - 3\ y\^2 - 16] == 2\ \@\(7\/3\), x == 2\ \@\(7\/3\)}, {x, > \ > \(-5\), 5}, {Function[x, x\^2 + 2\ xy - 3\ y\^2 - 16], \(-5\), 5}]\) > > > > What am I doing wrong? Even ImplicitPlot[x+y==2,{x,-4,4}] fails. > > Thanks > > > > ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.

**References**:**ImplicitPlot errors***From:*"David Rees" <w3bdevilREMOVE@THISw3bdevil.com>