Just Observe it !!!!

Consider a function:

$f\left( x \right) =a\log { \left( \frac { 1+x }{ 1-x } \right) } +b{ x }^{ 3 }+c\sin { x } +5$

And it is given that $f\left( \log _{ 3 }{ 2 } \right)=4$ , then find the value of $f\left( \log _{ 3 }{ \left( \frac { 1 }{ 2 } \right) } \right)$

$\bullet$ Here $a$ and $b$ are constants.

$\bullet$ Just observe closely and you will get it.....It's Easy!!!!!!!!