integrate.c implements four numerical integration procedures including:
    - The trapezoid rule
    - Simpson's one-third rule
    - Simpson's three-eighths rule
    - Boole's rule

Each function takes as arguments:
   - a pointer to a function with one argument (i.e. f(x))
   - the left bound on the interval of integration
   - the right bound on the interval of integration
   - the number of samples to perform on the interval

See main.c for an example.