clear all;
x = -2*(pi):0.4:2*(pi);
y = -2*(pi):0.4:2*(pi);
[xx, yy] = meshgrid(x,y);
g = @(xx,yy) log(2*cosh(yy)+sqrt(3)*cos(xx));
zz = g(xx,yy);
contour(xx,yy,zz);
xlabel('x');
ylabel('y');
zlabel('z');
axis equal;