printf more equal than sin?

[Holger Blasum]

On 10-23, Carlos O'Donell wrote:
> I don't understand what you are asking. Could you please clarify your question?

If I run gcc, "sin"(math.h) needs "-lm".
If I run gcc, "printf"(stdio.h) needs nothing (internally gcc uses "-lc", but
I do not need to know this). 

Where does it say that sin needs "-lm" (as opposed to printf needing
nothing or, internally only, "-lc") in the glibc documentation?

-- 
Holger