d3r1.cpp

visual c++查过能用数值算法 附带光盘里面的源代码

#include "iostream.h"
#include "math.h"

double func(double x)
{
    return pow(x, 2) * (pow(x,2) - 2.0) * sin(x);
}

double fint(double x)
{
    //integral of func
	double aaa;
    aaa = 4.0 * x * (pow(x,2) - 7.0) * sin(x);
    return aaa - (pow(x , 4) - 14.0 * pow(x , 2) + 28.0) * cos(x);
}

void main()
{
    //program d3r1
    //driver for routine trapzd
	int i;
    const int nmax = 14;
    double pio2 = 1.5707963;
    double s,b,a = 0.0;
    b = pio2;
    cout<<endl;
    cout<<"integral of func with 2^(n-1) points"<<endl;
    cout<<"actual value of integral is: ";
    cout<<(fint(b) - fint(a))<<endl;
    cout<<endl;
    cout<<"      n     approx.integral"<<endl;
	cout.setf(ios::fixed|ios::right);
	cout.precision(6);
    for (i = 1; i<=nmax; i++)
	{
        trapzd(a, b, s, i);
		cout.width(7);
        cout<<i;
		cout.width(16);
        cout<<s<<endl;
    }
}