C++ builder при компиляции выдаёт ошибку "Unresolved external 'fun2(double)' referensed from C:

//---------------------------------------------------------------------------
#include <math>
#pragma hdrstop
#include <conio.h>
#include <iostream.h>
//---------------------------------------------------------------------------
#pragma argsused
//================
typedef double (*TFun)(double);
double fun1(double);
double fun2(double);
void Out_Rez (TFun,double,double,double);
void main()
{
 double a, b, h;
 puts("Input a,b,h");
 scanf("%lf%lf%lf", &a, &b, &h);
 puts("\n\t Function - 2*(pow(cos(x),2)-1)"); Out_Rez (fun1,a,b,h);
 puts("\n\t Function - 3434"); Out_Rez (fun2,a,b,h);
 puts("\n Press any key ... ");
 getch();
}
//---------------------------------------------------------------------------
double fun1( double x){
return 2*(pow(cos(x),2)-1);
}
 
double fun2(double x, double n, double a, double b, double h){
double sum=0; int fk=1;  int k; int j;
 for (x=a; x<=b; x+=h) {
         for (k=1; k<=n; k++) {
                for (j=1; j<=2*k; j++) fk=fk*j;
               sum+=pow((-1), k)*pow(2.*x,2.*k)/(fk);}
return (sum);};}
 
 
void Out_Rez (TFun f,double xn,double xk,double h) {
for(double x=xn; x<=xk; x+=h)
printf(" x = %5.2lf, y = %8.4lf\n",x,f(x));
}