Re: Vertical Tangents

*To*: mathgroup at smc.vnet.net*Subject*: [mg25831] Re: Vertical Tangents*From*: "Allan Hayes" <hay at haystack.demon.co.uk>*Date*: Sat, 28 Oct 2000 01:41:23 -0400 (EDT)*References*: <8t64dv$egv@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Tom, You need to give ranges for both variables: << Graphics`ImplicitPlot` ImplicitPlot[{x^2 + x*y + y^2 == 7, y == 2*Sqrt[7/3], x == 2*Sqrt[7/3]}, {x, -5, 5}, {y, -5, 5}] -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 "Tom Moriarty" <tjmor at erols.com> wrote in message news:8t64dv$egv at smc.vnet.net... > This group was very helpful on my last question and I hope you will be > willing to once again come to the aid of a teacher trying to illustrate > to calculus students tangents to implicit plots. By the way, I > purchased Mathematica on my own, it is not available to me at school - > so I plot at home and Xerox handouts for the kids. I have been able to > show them various implicit plots and tangents to them - for example > ImplicitPlot[{x^2 + x*y + y^2==7, y == 2*Sqrt[7/3]},{x,-5,5}] which > clearly shows the ellipse and one of the horizontal tangents (as asked > for in the textbook problem). But the problem also asked for the > vertical tangents, one of which would be x == 2*Sqrt[7/3], but I get the > message that this equation does not have a single variable other than > x. Is there any way to plot a vertical line? > > Let me tell you Mathematica certainly has helped my students (and me) > visualize these implicit plots, without which they are just a matter of > faith. > > Any help you can give me will be greatly appreciated. > > Tom Moriarty > > >