% Example 12.4a (Physics 330)

function s=defint(a,b,N)

%*********************************************************
% this function uses the midpoint rule on N subintervals
% to calculate the integral from a to b of the function
% defined in the sub function at the bottom of this
% function

% load dx and build the midpoint rule x-values
%*********************************************************

dx=(b-a)/N;
x=a+.5*dx:dx:b-.5*dx;

%*********************************************************
% use the function f(x) defined in the sub function below
% to obtain the midpoint approximation to the integral and assign
% the result to s
%*********************************************************

s=sum(f(x))*dx;

% here's the sub function

function y=f(x)

% define the function f(x) and assign it to y

y=cos(x);

%end defint.m