tested:
lib size: 17908byte (only using f_sin(), f_sd and f_to_string)
using all trigonometric set plus f_add, f_sub and f_mult is 24238 byte
this trigonometric formula using float execute in 1ms, with this lib 50ms.
but seems like sin is wrong, it doesn't give the right value.
The bignumber lib doesn't have the trig function i need (sin, cos, atan2)