Matlab - Ayuda Cuadratura Gauss-Legendre en MATLAB

function y=GL4(f,a,b)

x1=sqrt(1/3);

x2= -sqrt(1/3);

t1=(a+b)/2+(b-a)/2*x1;

t2=(a+b)/2+(b-a)/2*x2;

y=(f(t1)+f(t2))*(b-a)/2;

>> y=double(int(sym('x^2'),1,2))

y =

    2.3333

>> y=double(GL4('x^2',1,2))

y =

    2.3333

function y=GL4(f,a,b)

syms x

x1=sqrt(1/3);

x2= -sqrt(1/3);

t1=(a+b)/2+(b-a)/2*x1;

t2=(a+b)/2+(b-a)/2*x2;

y=double((subs(f,x,t1)+subs(f,x,t2))*(b-a)/2);

>> y=GL4('x^2',1,2)

y =

    2.3333