Where is mathimf.h when using MS C++?

#include <stdio.h>
#include <Mkl.h>
#include <Math.h>

//#include <Mathimf.h>	// cannot open

int main() {
	printf("Bessel J0(5)\t%1.19f\n", j0(5.0));	// testing MKL ******************************
}

Works like a charm, although I expected j0() to reside in Mathimf.h - but that file is not present on my machine... any idea why?

Questions:

1. When using Math.h instead of the non-existent MathImf.h, will my program use the slow old MS C++ j0()?

2. Does the true MKL j0() reside somewhere else?

3. I would like to use LoadLibrary & GetProcAddress. Is there a DLL in C:\Program Files (x86)\IntelSWTools\compilers_and_libraries\windows\redist\ia32\mkl\ that contains this Bessel function?