syms x y z; h=x^2+y^2+z^2; clf; % Clear old figure
implicitplot3d(h, 3, -3, 3, -3, 3, -3, 3, 200); axis equal
%implicitplot3d(h, 3, -3, 3, -3, 3, -3, 3, 150); 
%implicitplot3d(h, 1, -3, 3, -3, 3, -3, 3, 70); 
%implicitplot3d(h, 2, -3, 3, -3, 3, -3, 3, 40);
%implicitplot3d(h, 3, -3, 3, -3, 3, -3, 3, 40);
%implicitplot3d(h, 4, -3, 3, -3, 3, -3, 3, 40);
%implicitplot3d(h, 5, -3, 3, -3, 3, -3, 3, 40); 
point=[1,1,1];
plot3(1,1,1,'rs')
grad = 2*point;
k = -3:0.01:3;
line = point'*ones(size(k)) + grad'*k;
plot3(line(1,:),line(2,:),line(3,:));

line = point'*ones(size(k)) + [1,2,3]'*k;
plot3(line(1,:),line(2,:),line(3,:));
hold off; 
