1>main.obj : error LNK2019: unresolved external symbol "public: __thiscall NewTriangle::~NewTriangle(void)" ([email="??1NewTriangle@@QAE@XZ"]??1NewTriangle@@QAE@XZ[/email]) referenced in function [email="_WinMain@16"]_WinMain@16[/email]
1>main.obj : error LNK2019: unresolved external symbol "public: __thiscall NewTriangle::NewTriangle(void)" ([email="??0NewTriangle@@QAE@XZ"]??0NewTriangle@@QAE@XZ[/email]) referenced in function [email="_WinMain@16"]_WinMain@16[/email]
[/quote]

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[color="#ff0000"]EDIT: The newer attachment is at Post #3 (below ryan20fun's post).

The main problem is that, the NewTriangle is a class. A class that have all member functions defined in its CPP file. As for the main.cpp in the ZIP file, I commented out some lines, just to try and invoke the creation and deletion of NewTriangle class.

If the commented part were uncommented, then it would give 2 more LNK2019 errors to the same NewTriangle class, which is why I couldn't solve it out. So, I really don't know how to solve it, and I would like for some help. Tips would be awesome.

i cannot load the project, the vcxproj file is missing,
can you upload it ?

The new ZIP file still seems to be incomplete. The project contains core.h/core.cpp and triangle.h/trangle.cpp, which are all missing from the ZIP. And NewTriangle.h/NewTriangle.cpp are in the ZIP file, but are not part of the project when it is loaded up.