>> y=x*exp(-x)*sin(x);
>> y1=diff(y,x);
>> y2=diff(y1,x);
>> y3=diff(y2,x);
>> y4=diff(y3,x);
>> ezplot(y),hold on;
>> ezplot(y1),hold on;
>> ezplot(y2),hold on;
>> ezplot(y3),hold on;
>> ezplot(y4),hold on;
>> legend('y','dy/dx','dy^2/dx^2','dy^3/dx^3','dy^4/dx^4')
>> gtext('y=x*exp(-x)*sin(x)')
