Solving nonlinear equations by gradient descent method

#include <math.h> #include <iostream> using namespace std;
void Newton (int n,double x[],double y[],double eps);
DOUBLE fn (int n,double x[],double y[]);
Const double PI = 3.14159265358979323846;
	int main () {int i,n=3;
	Double y[3],x[3]={0.5,0.5,0.5};
	Double eps=1.e-08;	
	Newton (N,X,Y,EPS);
	for (i=0;i<n;i++) {cout<<i<< "" <<x[i]<< "" <<y[i]<<endl;
} return 0;
	} double fn (int n,double x[],double y[]) {double s2=0.0;
	Y[0]=3.0*x[0]-cos (x[1]*x[2])-1.5;
	Y[1]=4*x[0]*x[0]-625*x[1]*x[1]+2*x[2]-1;
	Y[2]=exp (-x[0]*x[1]) +20*x[2]+ (10*pi-3)/3.0;
	for (int i=0;i<n;i++) {s2+=y[i]*y[i];
} return s2;
	} void Newton (int n,double x[],double y[],double eps) {double s[3],s0,s1,s2,t,alpha,h=1.e-05;
		while (1) {S2=FN (n,x,y);
		S0=S2;
		if (s0<eps) break;
		s1=0.0;
			for (int i=0;i<n;i++) {t=x[i];
			x[i]= (1.0+h) *t;
			S2=FN (N,x,y);
			s[i]= (S2-S0)/(H*T)///???
			S1+=s[i]*s[i];
		x[i]=t;
		} alpha=s0/s1; for (int i=0;i<n;i++) {x[i]-=alpha*s[i];
		cout<<i<< "" <<x[i];
	} cout<<endl; }

}