musl

If you're being technical, it's usually not a Taylor series, it's a minimax series. (The difference is that Taylor series minimize error at a given value, whereas minimax is trying to minimize maximum error in a range). In most general math library implementations (e.g., the library in glibc, musl, etc.), the implementation of sin, as with most functions, is going to be a polynomial evaluation. See, e.g., https://github.com/kraj/musl/blob/kraj/master/src/math/__cos... for the implementation in musl, or https://github.com/bminor/glibc/blob/master/sysdeps/ieee754/... for glibc's implementation. Of course, if you're not using a standard math library implementation, you're probably preferring speed over accuracy, and so you might use a lookup table and linear interpolation to get a very coarse approximation instead.

There's also the other 'old-school' method to compile each function into its own object file, I guess that's why MUSL has each function in its own source file: https://github.com/kraj/musl/tree/kraj/master/src/stdio ...but these days -flto is simply the better option to get rid of unused code and data - and enable more optimizations on top. LTO is also exactly why static linking is strictly better than dynamic linking, unless dynamic linking is absolutely required (for instance at the operating system boundary).