How can i mark the points in a surface that have a certain value?

Hi all,

I am carrying out a project in which I have to find a stationary configuration, which sums up into solving a non linear sysyem of equations of sinusoidal functions where the functions (which have to be equal to 0) are:

2*cos(x)*(8*sin(x)+3*sin(y))-9*sin(x)=0 2*cos(y)*(3*sin(x)+2*sin(y))-3*sin(y)=0

The main thing is that I want to plot both equations in the whole domain (0X2pi,0X2pi) so I can show all the possible solutions (although I will focus on the first cuadrant solutions)

To plot the firts function i use

ezsurf('2*cos(x)*(8*sin(x)+3*sin(y))-9*sin(x)',[0,2*pi],[0,2*pi],100)

There is any way I can mark in the surface, all the 0 values (i.e. solution points?)

Thank you very much for your time.

Answer 1

[Chad Greene]

You have only plotted one data point that actually equals zero. I've labeled it with yellow text. To plot the contours at z=0, extract the x,y,z data from ezsurf:

h = ezsurf('2*cos(x)*(8*sin(x)+3*sin(y))-9*sin(x)',[0,2*pi],[0,2*pi],100); 
shading interp
hold on 

x = get(h,'xdata') ;
y = get(h,'ydata') ;
z = get(h,'zdata') ;

ind = z==0;
plot3(x(ind),y(ind),0,'yp')
text(x(ind),y(ind),'Z = 0','fontweight','bold','color','y')

contour(x,y,z,[0 0],'magenta','linewidth',4)

[Jaume]

Thank you very much! It has been really helpful!

[Image Analyst]

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