/ 2/x\ \
| sin |-| |
| \3/ | /x\
|1 - -----------|*cos|-|
| 2/x\| \3/
| 1 - cos |-||
\ \3//
------------------------
_____________
/ 2/x\
9* / 1 - cos |-|
\/ \3/
$$\frac{\left(1 - \frac{\sin^{2}{\left(\frac{x}{3} \right)}}{1 - \cos^{2}{\left(\frac{x}{3} \right)}}\right) \cos{\left(\frac{x}{3} \right)}}{9 \sqrt{1 - \cos^{2}{\left(\frac{x}{3} \right)}}}$$
/ 2/x\ 2/x\ 2/x\ 2/x\\
| sin |-| 3*cos |-| 3*cos |-|*sin |-||
| \3/ \3/ \3/ \3/| /x\
|-1 + ----------- - ----------- + -----------------|*sin|-|
| 2/x\ 2/x\ 2 | \3/
| 1 - cos |-| 1 - cos |-| / 2/x\\ |
| \3/ \3/ |1 - cos |-|| |
\ \ \3// /
-----------------------------------------------------------
_____________
/ 2/x\
27* / 1 - cos |-|
\/ \3/
$$\frac{\left(-1 + \frac{\sin^{2}{\left(\frac{x}{3} \right)}}{1 - \cos^{2}{\left(\frac{x}{3} \right)}} - \frac{3 \cos^{2}{\left(\frac{x}{3} \right)}}{1 - \cos^{2}{\left(\frac{x}{3} \right)}} + \frac{3 \sin^{2}{\left(\frac{x}{3} \right)} \cos^{2}{\left(\frac{x}{3} \right)}}{\left(1 - \cos^{2}{\left(\frac{x}{3} \right)}\right)^{2}}\right) \sin{\left(\frac{x}{3} \right)}}{27 \sqrt{1 - \cos^{2}{\left(\frac{x}{3} \right)}}}$$