Numerisches Trapez-Integral

function plot_trapez()
f = @sin;
a = 0;
b = pi;
fehler = [];
n_values = 1e3:100:1e4;
for n=n_values
    fehler(end+1) = abs(2-trapez(f,a,b,n));
end
plot(n_values, fehler)
end

function I = trapez(f,a,b,n)
h = (b-a)/n;
x0 = a/2;
xn = (a+n*h)/2;
I = h*(f(x0) + f(xn));
for j=1:n-1
    xj = a + j*h;
    I = I + f(xj);
end
end