/ sin(x) |sin(x)|
| -------------- for -------- < 1
| / sin(x)\ 3
| 3*|1 - ------|
| \ 3 /
|
< oo
| ___
| \ `
| \ -n n
| / 3 *sin (x) otherwise
| /__,
\n = 1
$$\begin{cases} \frac{\sin{\left(x \right)}}{3 \left(1 - \frac{\sin{\left(x \right)}}{3}\right)} & \text{for}\: \frac{\left|{\sin{\left(x \right)}}\right|}{3} < 1 \\\sum_{n=1}^{\infty} 3^{- n} \sin^{n}{\left(x \right)} & \text{otherwise} \end{cases}$$
Piecewise((sin(x)/(3*(1 - sin(x)/3)), Abs(sin(x))/3 < 1), (Sum(3^(-n)*sin(x)^n, (n, 1, oo)), True))