Basically, what i am trying to do, is write a program that will integrate a function using the rectangle method.

I'm fine with the maths part.

And i can declare a function within the actual file. What i would love to do, in the end is to be able to run the program, be able to input any function (of x - say x^2, or x^3 - 3x for example), and then integrate this by the chosen method.

At the minute, i can only change the function within the cpp pile, and not within the program.

Any suggestions would be great. I am a fairly newcomer to C++ so sorry if i don't grasp what is needed!!

I thought maybe i could get the program to first ask u to input the function, and save that in a seperate file, and then later on it can call on that saved file and read from it the function thats been inputted.

Anyway, here is what i have:

Code:#include <iostream.h> #include <iomanip.h> #include <math.h> #include <fstream.h> float funcj(float); float main() { int n, i; float a, b, h, x, s, integral; i = 0; cout << "Please input a, the lower bound: "; cin >> a; cout << "\nPlease input b, the upper bound: "; cin >> b; if (a >= b) { cout << "\nYou have inputted the data incorrectly. Please try again.\n"; } else { integral = 0; cout << "\nPlease input the number of strips required: "; cin >> n; { h = fabs(a - b) / n; while ( i < n) { x = a + i * h; s = h * funcj(x); integral = integral + s; i++; } cout <<"\nThe answer is: " << integral; } } } float funcj(float x) { float f; f = (x*x) - (5*x) - 3 ; return f; }