sketch the graph of the function: f(x,y)= 1+2x^2+2y^2

I'm not sure how to plot above equation. Can anyone help me?

Answer 1

[Jan]

fsurf(@(x,y) 1 + 2 * x.^2 + 2 * y.^2)

[Ta Duc]

I don't think your answer is correct because it's different from the answer. Can u help me to do it again, tks a lot!

[Jan]

@Ta Duc: Where do you see a difference? Matlab crops the object at rectangluar limits of the axis, in your image the object is cropped at a specific z value. Both methods are valid ways to display the object.

Do you see, that the formulas are identical?

Answer 2

[Carlos Guerrero García]

The usage of polar coordinates must be useful:

[rho,theta]=meshgrid(0:0.1:2,0:pi/60:2*pi);
x=rho.*cos(theta);
y=rho.*sin(theta);
z=1+2*x.^2+2*y.^2;
surf(x,y,z);
shading interp; 
axis equal % for a nice view