// Example of for loops to compute a derivative.
// derive.cpp
// ESC 104

#include <iostream.h>
#include <iomanip.h>

main()
	{
	double x;
	double f_of_x;
	double f_of_xh;
	double derivative;
	int i;
	double h = 0.00001;

	cout << setprecision(4)
		  << setiosflags( ios::fixed | ios::showpoint );

	for( i=0; i<20; i++)
		{
		x = (double)i;
		f_of_x = 2*x*x + 3*x + 4;

		x += h;
		f_of_xh = 2*x*x + 3*x + 4;

		derivative = (f_of_xh - f_of_x )/h;

		cout << "Derivative at x = " << (x-h) << " is " << derivative << endl;
	}

	return 0;
	}