Composite Trapezoid Rule
In numerical analysis, the trapezoidal rule is used for approximation of a definite integral. The code here is a general purpose code for any equation. 
function integral = trapezoid(f, a, b, n)
x = (b-a)/n; result = 0.5*f(a) + 0.5*f(b); for i = 1:(n-1) result = result + f(a + i*x); end integral = x*result;
f is the equation, a is the lower limit, b is the upper limit, and n is the number of trapezoids or number of integration points.