[Dev-C++] Importing DLL Functions

[Samuel H. <tal...@gm...>]

Hi,
For so long I have been using a different compiler, but now I am using 
Dev-C++, In my old compiler I was able to create a header file and place 
something like this in it:

 > double hypotenuse(double sidea,double sideb);

Then include it into my app, set the .a file and use it, but now I get 
an error message saying:

 >  [Linker error] undefined reference to `hypotenuse(double, double)'

Any ideas?