identifying the critical points of a bivariate function

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ektor 2020-3-9

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https://ww2.mathworks.cn/matlabcentral/answers/509942-identifying-the-critical-points-of-a-bivariate-function

编辑： ektor 2020-3-9

Dear all,

I have this function below and I plotted it in a 3D space. Is it possible to mark the critical points on the graph so as to be visible to the reader? Similarly for the max or min value of the function?

Best

syms x y
f = 4*x.^2+3*y.^2 ;
   
     
 
    fx = diff(f,x);
    fy = diff(f,y);
 
    [xc,yc] = solve(fx,fy,x,y); [xc,yc];
     fxx = diff(fx,x); fxy = diff(fx,y); fyy = diff(fy,y);
    D = fxx*fyy - fxy^2;
     subs(D,{x,y},{xc(1),yc(1)});
    subs(fxx,{x,y},{xc(1),yc(1)});
 
 
    figure(1); ezsurf(f,[-10,50,-10,50]);