source for math functions?

Hi guys, this subject is a bit of topic and I am sorry in advance... I
am trying to figure out how math functions like pow exp log etc are
implemented in the C++ stl lib for example (cmath or math.h). So that I
thought I might be able able to figure out by looking at their
implementation under linux as the source code is available. But of
course the source tree is huge so I was wondering if someone could
point me to the right files (which lib I should look into).
Many thanks, mark

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