Hi Minifriese,
kleiner Auszug aus der avr-libc:

Functions
double cos (double __x) __ATTR_CONST__
double fabs (double __x) __ATTR_CONST__
double fmod (double __x, double __y) __ATTR_CONST__
double modf (double __value, double *__iptr)
double sin (double __x) __ATTR_CONST__
double sqrt (double __x) __ATTR_CONST__
double tan (double __x) __ATTR_CONST__
double floor (double __x) __ATTR_CONST__
double ceil (double __x) __ATTR_CONST__
double frexp (double __value, int *__exp)
double ldexp (double __x, int __exp) __ATTR_CONST__
double exp (double _x) __ATTR_CONST__
double cosh (double __x) __ATTR_CONST__
double sinh (double __x) __ATTR_CONST__
double tanh (double __x) __ATTR_CONST__
double acos (double __x) __ATTR_CONST__
double asin (double __x) __ATTR_CONST__
double atan (double __x) __ATTR_CONST__
double atan2 (double __y, double __x) __ATTR_CONST__
double log (double __x) __ATTR_CONST__
double log10 (double __x) __ATTR_CONST__
double pow (double __x, double __y) __ATTR_CONST__
int isnan (double __x) __ATTR_CONST__
int isinf (double __x) __ATTR_CONST__
double square (double __x) __ATTR_CONST__
double inverse (double) __ATTR_CONST__

von daher dürften die Grundrechenarten kein Problem sein