trapezoid1.cpp

这是一个用梯形法求积的程序实例（VC）

//Trapezoid method of Integration
//This is the definite step version of c++

#include <iostream.h>
#include <math.h>

int N;	//ensure the step

//-----------integrated fuction-------------
double f(double x)
{
	return exp(x)/(1+x*x);
}
//------------------------------------------

//-----------definite step version----------
double trapezoid(double a,double b,double (*f)(double))
{
	double h=(b-a)/N;
	double x=b;
	double trap=f(x);

	x=a;
	trap+=f(x);
	trap/=2;
	for(int i=1;i<N;i++)
	{
		x=a+i*h;
		trap+=f(x);
	}
	trap*=h;

	return trap;
}
//------------------------------------------

//-----------------main---------------------
void main()
{
	double x,y;
	
	cout<<"enter the lower limit,upper limit & N"<<endl;
	cin>>x>>y>>N;

	cout<<"The Integration(T method): "<<trapezoid(x,y,f)<<endl;
}
//------------------------------------------