To plot the surface “z = x^2 - 2y^2”, the surf command can be utilized as follows:
surf(x, y, z, 'EdgeColor', 'none', 'FaceAlpha', 0.7);
For plotting the cylinder “x1^2 + y1^2 = 4”, a stack of circles can be created and plotted using plot3 function in 3D. First, define the height for the cylinder and space the points equally to create a stack of circles:
height = linspace(-10, 10, 10000);
Then, iterate through the height values and plot the circles:
for k = 1:length(height)
plot3(x1, y1, height(k) * ones(size(x1)), 'r', 'LineWidth', 1.5);
end
The plot3 function can be used to plot the intersection surface as well.
z_intersection = x1.^2 - 2*y1.^2;
plot3(x1, y1, z_intersection);
Using sample data, the image obtained is as follows:

For more information, you can refer to the following documentation: