% matlab code
% use rectangular method for integration
f=inline("cos(10*x)"); % define function to integrate
x0=-1; %integral lower boundary
x1=1; % integral upper boundary
N=1000; % number of sub intervals
dx=(x1-x0)/N; % witdh of each sub interval
% integrate
S=0.0;
for i=0:N
x=x0+dx*i;
S=S+f(x)*dx;
end
% calculate the error for the case f(x)=cos(10 x)
err=sin(10)/5-S;