Using the result of Q6, deduce the lower bound $R \geqslant \pi/2$ for the radius of convergence $R$ of the power series $\sum_{n \in \mathbb{N}} \frac{\alpha_n}{n!} x^n$.
Using the result of Q6, deduce the lower bound $R \geqslant \pi/2$ for the radius of convergence $R$ of the power series $\sum_{n \in \mathbb{N}} \frac{\alpha_n}{n!} x^n$.