Need help with calculating this sum: $\sum_{n=0}^\infty\frac{1}{2^n}\tan\frac{1}{2^n}$
I need help with calculating this sum: $$\sum_{n=0}^\infty\frac{1}{2^n}\tan\frac{1}{2^n}$$
Hint: use the fact that $\cot{x}-2\cot{2 x}=\tan{x}$
i just was reading this book yesterday
