Re: Vertical Tangents

*To*: mathgroup at smc.vnet.net*Subject*: [mg25806] Re: Vertical Tangents*From*: Albert Retey <albert.retey at visualanalysis.com>*Date*: Sat, 28 Oct 2000 01:41:00 -0400 (EDT)*Organization*: Visual Analysis*References*: <8t64dv$egv@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Tom Moriarty wrote: > > 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? I don't have expericence with ImplicitPlot, so I don't know whether you can make it plot what you need, but a simple way to produce a vertical line is: p = ParametricPlot[{2*Sqrt[7/3], t}, {t, -10, 10}] Then use Show to put it together with your ImplicitPlots Albert