colormap('jet')
f=@(x,y)x.*(e.^(-x.^2-y.^2));
x=-2:0.2:2;
y=-2:0.2:2;
[x1,y1]=meshgrid(x,y);
z=f(x1,y1);
subplot(2,2,1);
surf(x,y,z);
title('graph1');
%b

f=@(x,y)3.*sin(x).*cos(y);
x=-5:81;
y=0:81;
[x1,y1]=meshgrid(x,y);
z=f(x1,y1);
subplot(2,2,2);
surf(x,y,z);
title('graph2');
%c
f=@(x,y)(sin(sqrt(x.^2+y.^2)))/(sqrt(x.^2+y.^2)+0.1);
x=-8:0.2:8;
y=-8:0.2:8;
[x1,y1]=meshgrid(x,y);
z=f(x1,y1);
subplot(2,2,[3 4]);
surf(x,y,z);
title('graph3');