void main()
{
long double FNF(long double, long double);
fstream out_file; //creates variable for a file
long double x1=1,h=0,x0=0,y0=0,k=0,k1=0,k2=0,k3=0,k4=0;
long double x=0,y=0; //initial x y
int n=0; //number of steps
out_file.open("c:\\windows\\desktop\\rungekut.txt",ios::out);//opens a file for output
cout <<"y= ? ";
cin >> y;
cout <<"\nx= ? ";
cin >> x;
cout <<"\nn= ? ";
cin >> n;
h= (x1-x)/n; //step size
for(int i=1; i<=n; i++)
{
x0=x;
y0=y;
k1= FNF(x,y); //call function
x= x0 + h/2;
y = y0+ h*k1/2;
k2= FNF(x,y); //call function
y= y0 + h*k2/2;
k3 = FNF(x,y); //call function
x= x0+h;
y= y0+ h*k3;
k4= FNF(x,y); //call function
k= (k1 + 2*k2 + 2*k3 + k4)/6;
y = y0 + h*k;
cout.precision(10);
out_file.precision(10);
cout << "\nx= " << x << " y= " << y << " "; //output
out_file << "\nx= " << x << " y= " << y << " "; //output to a file for printing
}
out_file.close();//closes out put file
char hold;
cout <<'\n';
cin >> hold;
return;
}
Fonc_Num SurfIER_Fonc_Num_Not_Comp::deriv(INT k) const
{
ELISE_ASSERT(mFctr==SurfIER,"SurfIER_Fonc_Num_Not_Comp::deriv");
return
fCEl.x.deriv(k) * FNF("DerCElXSurfIER",DerCElXSurfIER)
+ fCEl.y.deriv(k) * FNF("DerCElYSurfIER",DerCElYSurfIER)
+ fA.deriv(k) * FNF("DerASurfIER",DerASurfIER)
+ fB.deriv(k) * FNF("DerBSurfIER",DerBSurfIER)
+ fC.deriv(k) * FNF("DerCSurfIER",DerCSurfIER)
+ fP0.x.deriv(k) * FNF("DerP0XSurfIER",DerP0XSurfIER)
+ fP0.y.deriv(k) * FNF("DerP0YSurfIER",DerP0YSurfIER)
+ fP1.x.deriv(k) * FNF("DerP1XSurfIER",DerP1XSurfIER)
+ fP1.y.deriv(k) * FNF("DerP1YSurfIER",DerP1YSurfIER);
}
