Show that $$\forall x \in ]-1,1[ \quad s(x)e^{x} = \frac{1}{1-x}$$ Deduce that $R = 1$.
Show that
$$\forall x \in ]-1,1[ \quad s(x)e^{x} = \frac{1}{1-x}$$
Deduce that $R = 1$.