Динамическая загрузка библиотеки

#include <windows.h>
#include <math.h>
 
extern "C"  __declspec(dllexport) double MyFunc(double X, double Y)
{
    return -log(fabs(X * X / (Y - 1))) / log(2.0);
}

#include "stdafx.h"
#include <iostream>
 
#pragma comment(lib, "lab2.lib") 
extern "C" _declspec(dllexport) double MyFunc( double X, double Y);
using namespace std;
 
int _tmain(int argc, _TCHAR* argv[])
{
    setlocale(LC_ALL, "Russian");
    double X, Y;
    cout << "Введите X: ";
    cin >> X;
    cout << "Введите Y: ";
    cin >> Y;
    cout << "Результат = " << MyFunc(X, Y) << endl;
    system("pause");
    return 0;
}

#include <iostream>
#include <Windows.h>
using namespace std;
 
int main(int argc, CHAR* argv[])
{
    setlocale(LC_ALL, "Russian");
    double X, Y;
    cout << "Введите X: ";
    cin >> X;
    cout << "Введите Y: ";
    cin >> Y;
    HINSTANCE hDllInstance = LoadLibraryEx(L"lab2.dll", 0, DONT_RESOLVE_DLL_REFERENCES );
    typedef double(*functionDll)( double, double );
    functionDll myFunc = (functionDll)GetProcAddress(hDllInstance, "MyFunc");
    cout << "Результат = " << myFunc(X, Y) << endl;
    FreeLibrary(hDllInstance);
    system("pause");
    return 0;
}

#include <windows.h>
#include <math.h>
 
extern "C"  __declspec(dllexport) double MyFunc(double X, double Y)
{
    return 5;
}

extern "C"  __declspec(dllexport) double MyFunc(double X, double Y)
{
    double res = -log(fabs(X * X / (Y - 1))) / log(2.0); 
    return 5;
}

#include <windows.h>
#include <math.h>
 
extern "C"  __declspec(dllexport) double MyFunc(double X, double Y)
{
    //double res = -log(fabs(X * X / (Y - 1))) / log(2.0); 
    return fabs(-5.0);
}

HINSTANCE hDllInstance = LoadLibraryEx(L"lab2.dll", 0, DONT_RESOLVE_DLL_REFERENCES );
 
if (hDllInstance == NULL){
   cout << "hDllInstance == NULL" << << endl;
}
 
    typedef double(*functionDll)( double, double );
    functionDll myFunc = (functionDll)GetProcAddress(hDllInstance, "MyFunc");
 
if (myFunc == NULL){
   cout << "myFunc == NULL" << << endl;
}

HINSTANCE hDllInstance = LoadLibraryEx(L"lab2.dll", 0, DONT_RESOLVE_DLL_REFERENCES );
 
    if (hDllInstance == NULL){
        cout << "hDllInstance == NULL" << endl;
    }
 
    typedef double(*functionDll)( double, double );
    functionDll myFunc = (functionDll)GetProcAddress(hDllInstance, "MyFunc");
 
    if (myFunc == NULL)
    {
        cout << "myFunc == NULL" << endl;
    }
    else
    {
    cout << "Результат = " << myFunc(X, Y) << endl;
    }