function graf_3D_2
x=linspace(0,pi,30);
y=x;
[X,Y]=meshgrid(x,y);
Z=sin(X+Y);
subplot(1,2,1)
surf(X,Y,Z)
subplot(1,2,2)
mesh(X,Y,Z)
hold on
contour3(X,Y,Z,'k')
hold off
end

