function plosny3Dgraf3
x=linspace(-5,5,15);
y=x;
[X,Y]=meshgrid(x,y);
Z=sin(sqrt(X.^2+Y.^2))./sqrt(X.^2+Y.^2);
subplot(2,2,1)
mesh(X,Y,Z)
subplot(2,2,3)
contour(X,Y,Z)
[F,G]=gradient(Z);
hold on
quiver(x,y,F,G)
hold off
subplot(2,2,2)
mesh(X,Y,-Z)
subplot(2,2,4)
contour(X,Y,-Z)
[F,G]=gradient(-Z);
hold on
quiver(x,y,F,G)
hold off
end

