function t=trap(f,a,b,n)
% f is a string denoting an availible function
h=(b-a)/n;
x=a+h:h:b-h;
y=feval(f,x);
z=sum(y);
t=h*(2*z+feval(f,a)+feval(f,b))/2;

function s=simp(f,a,b,n)
% f is a string denoting an available function
h=(b-a)/n;
x1=a+h:2*h:b-h;
x2=a+2*h:2*h:b-2*h;
y1=feval(f,x1);
y2=feval(f,x2);
z=4*sum(y1)+2*sum(y2);
s=h*(z+feval(f,a)+feval(f,b))/3;