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Vertical Tangents

  • To: mathgroup at
  • Subject: [mg25787] Vertical Tangents
  • From: Tom Moriarty <tjmor at>
  • Date: Wed, 25 Oct 2000 03:53:45 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

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

Any help you can give me will be greatly appreciated.

Tom Moriarty

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