Extra Math
This library aims at making available to Modelica some of the mathematical functions
that are defined in the C99 standard,
but that do not yet have a definition in the Modelica Standard Library (MSL).
A description of mathematical functions in C is given on Wikipedia:
https://en.wikipedia.org/wiki/C_mathematical_functions
Support for these functions will depend on many things, including operating system, compiler, C version and more.
This library will therefore not work everywhere,
and this is probably the reason why these functions are not included in the MSL.
Windows
Microsoft extended their support for C99 a lot in Visual Studio 2013:
http://blogs.msdn.com/b/vcblog/archive/2013/07/19/c99-library-support-in-visual-studio-2013.aspx
Documentation for what mathematical functions are supported can be found here:
https://msdn.microsoft.com/library/hh553049.aspx
or in the Visual Studio math.h header file, usually here:
C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\include\math.h
Linux
At least the compiler flag -std=c99 (or -std=gnu99) should be set for the compilers gcc and clang
to support the C99 standard.