# Contour3Dplot more graphs in one picture [duplicate]

How can I plot two equations in one 3D graph. I have to plot x^2+y^2=1 and x^2+y^2+z^2=2 but I want tu plot only their intersection :(

Thank you

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## marked as duplicate by Ｊ. Ｍ.Apr 20 '13 at 12:56

There were many similar questions so most likely this is a duplicate e.g. take a look at this : mathematica.stackexchange.com/questions/5968/…. Perhaps another hint : mathematica.stackexchange.com/questions/17799/… –  Artes Apr 20 '13 at 12:20
You are plotting x^2 + y^2 = 1. That's the unit circle. The second equation says 1+z^2=2, so z^2=1. Assuming we're talking about real numbers, this means either z=1 or z=-1. So your plot is: a unit circle at z=1 and another unit circle at z=-1. –  bill s Apr 20 '13 at 12:42

ContourPlot3D[{x^2 + y^2 - 1, x^2 + y^2 + z^2 - 2},