lim (x->0) x/sin x = 1
lim (x->0) (2^x - 1)/x = | 2^x = e^t => x = t/ln 2, t = x * ln 2 | = lim (t->0) (e^t - 1)/(t/ln 2) =
= ln 2 * lim (t->0) (e^t - 1)/t = ln 2