#include <iostream>
using namespace std;
#include<math.h>
#include<iomanip>
double calculateXr(double,double);
double calculatefx(double);
int main()
{
	double xl,xu,xr;
	cout<<"enter xl and xu: ";
	cin>>xl>>xu;
	cout<<"f(xl)= "<<calculatefx(xl)<<endl;
	cout<<"f(xu)= "<<calculatefx(xu)<<endl;
	xr=calculateXr(xl,xu);
	cout<<"xr= "<<xr<<endl;
	cout<<"f(xr)= "<<calculatefx(xr)<<endl;

system("pause");
return 0;

}
double calculateXr(double xl,double xu)
{
	return (xu-((calculatefx(xu)*(xl-xu))/(calculatefx(xl)-calculatefx(xu))));
}

double calculatefx(double x)
{
	double l=0.1;
	int k=240;
	int h=9;
	double efficiency=0.95;
	double A,P;
	A=x*x;
	P=4*x;
	double lamda,alpha;
	lamda=pow(((k*A)/(h*P)),0.5);
	alpha=pow((h*A)/(k*P),0.5);
	double a=sinh(l/lamda)+alpha*cosh(l/lamda);
	double b=cosh(l/lamda)+alpha*sinh(l/lamda);
	return(((a/b)*(lamda/(l+(A/P))))-0.95);
}