Qt Creator and using an external library under windows

I have a little problem with the Qt Creator and using an external library with windows.
I have installed successfully the current version of Qt Creator. For my Qt project, I want to use an additional scientific library for mathematics. This library is installed in the default windows folder c:\programme\...
In the system environment variables LIB and INCLUDE was added the path for the library (/lib and /include).
Now I have created a little Qt Project with a mainwindow.
In the created projectfile I have added the following:

win32:LIBS += c:\programme\sc\lib\sc.lib

In the next step, I have tried to include one of the several header files of the library, like this:

#include "interval.hpp" or
#include <interval.hpp>

When I compile the project, the problem "interval.hpp: No such file or directory" stopps the compiler.

I hope you have an answer for me for this little problem.

Thanks a lot,
QChristian

You need to tell the compiler where to find the header.

You can add the directory of interval.hpp to the project. See the project settings in Qt Creator