I have a hopefully simple question which I could not find any solution to yet: With two equations in three unkowns x,y,z I would like to plot their solution in x,y space. I cannot get rid of z explicitly and simply plot the resulting x,y equation as the functions are complicated. How can I tell Mathematica to do this graph for me?

  • $\begingroup$ Please provide your code! You can solve your problem using ContourPlot[Eliminate[eqn,z],{x,...},{y,...}] $\endgroup$ Nov 29, 2021 at 9:23
  • $\begingroup$ Thank you for the very fast reply. I would hate to copy paste the original equations as they are messy. Just assume y=lnz and x=(1/2)z (where I could simply eliminate of course). How does the command look like? $\endgroup$
    – Nafets
    Nov 29, 2021 at 9:34
  • $\begingroup$ ContourPlot[Eliminate[{y == lnz, x == 1/2 z}, z] {x, 0, 5}, {y, 0, 5}] did not work for me as the programme "expects more arguments". $\endgroup$
    – Nafets
    Nov 29, 2021 at 9:59
  • $\begingroup$ Related mathematica.stackexchange.com/questions/233870/… $\endgroup$
    – cvgmt
    Nov 29, 2021 at 11:08

1 Answer 1


With the correct syntax all works fine:

ContourPlot[Evaluate[ Eliminate[{y == Log[z], x == 1/2 z}, z]], {x, 0, 5}, {y, 0,5}] 

enter image description here

  • $\begingroup$ As always... Thank you Ulrich! $\endgroup$
    – Nafets
    Nov 29, 2021 at 10:06
  • $\begingroup$ Hope it helps solving your problem! $\endgroup$ Nov 29, 2021 at 10:16

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