Plotting a bivariate function and a tangent line on the same graph

Question

Scott Henley 2019-7-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/470980-plotting-a-bivariate-function-and-a-tangent-line-on-the-same-graph

回答： Star Strider 2019-7-10

I'm currently attempting to plot two functions, f(x,y) = x^2 + 3(x^2)y + 3 and 14(x-1) + 3(y-2) = 0, onto the same graph, however I'm finding extreme trouble (likely because of my inexperience) plotting the two simultaneously. The only part I understand thus far is that f(x,y) can't be converted to matrix form (required to plot in 3D) as it's not a linear function.

If someone is willing and able to walk me through the process of doing this, that would be greatly appreciated.

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Answer 1

Star Strider 2019-7-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/470980-plotting-a-bivariate-function-and-a-tangent-line-on-the-same-graph#answer_382606

在 MATLAB Online 中打开

To plot them simultaneously, you need to use the hold function.

See if this does what you want:

f = @(x,y) x.^2 + 3*(x.^2).*y + 3;                                  % Anonymous Function
g = @(x,y) 14*(x-1) + 3*(y-2);                                      % Anonymous Function
[X,Y] = ndgrid(linspace(-10,10, 250));                              % Define Matrix Arguments
figure
mesh(X, Y, f(X,Y))                                                  % Plot Surface
hold on
contour3(X, Y, g(X,Y), [0 0], 'Color','r', 'LineWidth',2)           % Plot Implicit Function
hold off
grid on
view(30,30)