I have an equation which is not analytically solvable,
thus I need to solve it numerically.
But, this equation has some free parameters which I want to replace them with some numbers after solving the equation

Let me ask a very simplified version of the question,
then I can solve the original one by the help of this simplified version.

I have an equation with the form of $a\space x^5+b\space sin(x)+3=0 $.
Now, I want to plot the root of this equation in the a-b coordinate system.

In another word,
I want to fix the root and see how it behaves by changing our free parameters, $a$ and $b$.


1 Answer 1


You can try ContourPlot3D:

ContourPlot3D[a x^5 + b Sin[x] + 3 == 0, 
  {a, -1, 1}, {b, -1, 1}, {x, -2 Pi, 2 Pi}, 

enter image description here

Alternatively, use ContourPlot to show combinations of a and b that make a given x the root and vary x interactively using Manipulate:

Manipulate[ContourPlot[a x^5 + b Sin[x] + 3 == 0, {a, -1, 1}, {b, -1, 1},  
     FrameLabel -> {"a", "b"}], 
  {{x, Pi/2}, -2 Pi, 2 Pi, Appearance -> "Labeled"}]

enter image description here

  • $\begingroup$ Thank you so much for your help. How can I transform this plot into two-dimensional a-b coordinate system for constant x? $\endgroup$
    – Mehrdad
    Jun 19, 2019 at 0:31
  • $\begingroup$ @Mehrdad, please see the updated version. $\endgroup$
    – kglr
    Jun 19, 2019 at 0:45

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