function [y] = rect(fun,a,b,n)
h=(b-a)/n;
k(1)=a;
k(n+1)=b;
sum=0;
for i=2:n
    k(i)=k(i-1)+h;
end
for j=1:n
    f=feval(fun,k(j));
    sum=sum+f;
end
y=sum*h;
end